Bearing device for a wheel

ABSTRACT

A bearing device for a wheel has a stem shaft of an outer joint member of a constant-velocity universal joint fit and inserted in a hole of a hub wheel, the stem shaft and hub wheel being coupled through an intermediation of a recess-projection fitting structure. Projections extending in an axial direction are provided on one of the stem shaft and an inner diameter surface of the hole of the hub wheel. The projections are press-fit into another of the stem shaft and the inner diameter surface of the hole along the axial direction. Recesses that adhere to and fit the projections are formed in the other. An end on an inboard side of the hub wheel is caulked to an outer diameter side to form a caulking section and preload is applied to a roller bearing by the caulking section.

TECHNICAL FIELD

The present invention relates to a bearing device for a wheel forsupporting wheels to freely rotate relative to a vehicle body in avehicle such as an automobile.

BACKGROUND ART

The bearing device for a wheel has evolved from a structure called firstgeneration in which roller bearings in double rows are independentlyused to second generation in which a vehicle body attachment flange isintegrally provided in an outer member. Further, third generation inwhich one inner raceway surface of the roller bearings in double rows isintegrally formed with an outer circumference of a hub wheel integrallyhaving a wheel attachment flange has been developed and fourthgeneration in which a constant-velocity universal joint is integratedwith the hub wheel and the other inner raceway surface of the rollerbearings in double rows is integrally formed with an outer circumferenceof an outer joint member configuring the constant-velocity universaljoint has been developed.

For example, the bearing device for a wheel called third generation isdescribed in Patent Document 1. The bearing device for a wheel calledthird generation includes, as illustrated in FIG. 39, a hub wheel 152having a flange 151 extending in an outer diameter direction, aconstant-velocity universal joint 154 having an outer joint member 153fixed to this hub wheel 152, and an outer member 155 disposed on anouter circumferential side of the hub wheel 152.

The constant-velocity universal joint 154 includes the outer jointmember 153, an inner joint member 158 disposed in a cup-shaped section157 of this outer joint member 153, a ball 159 disposed between thisinner joint member 158 and the outer joint member 153, and a retainer160 that retains this ball 159. A spline section 161 is formed on aninner circumferential surface of a center hole of the inner joint member158. An end spline section of a shaft (not shown) is inserted into thiscenter hole, whereby the spline section 161 on the inner joint member158 side and the spline section on the shaft side are engaged.

The hub wheel 152 has a cylindrical shaft section 163 and the flange151. A short-cylindrical pilot section 165, on which a wheel and a brakerotor (not shown) are mounted, is protrudingly provided on an outer endsurface 164 (end surface on an out board side) of the flange 151. Thepilot section 165 includes a large-diameter first section 165 a and asmall-diameter second section 165 b. The brake rotor is externally fitin the first section 165 a and the wheel is externally fit in the secondsection 165 b.

A notch section 166 is provided in an outer circumferential surface atan end on the cup-shaped section 157 side of the shaft section 163. Aninner ring 167 is fit in this notch section 166. A first inner racewaysurface 168 is provided near a flange on an outer circumferentialsurface of the shaft section 163 of the hub wheel 152. A second innerraceway surface 169 is provided on an outer circumferential surface ofthe inner ring 167. A bolt inserting hole 162 is provided in the flange151 of the hub wheel 152. A hub bolt for fixing the wheel and the brakerotor to this flange 151 is inserted into this bolt inserting hole 162.

In the outer member 155, outer raceway surfaces 170 and 171 in two rowsare provided on an inner circumference thereof and the flange (vehiclebody attachment flange) 151 is provided on an outer circumferencethereof. The first outer raceway surface 170 of the outer member 155 andthe first inner raceway surface 168 of the hub wheel 152 are opposed toeach other. The second outer raceway surface 171 of the outer member 155and the raceway surface 169 of the inner ring 167 are opposed to eachother. Rolling elements 172 are interposed between the second outerraceway surface 171 and the raceway surface 169.

A stem shaft 173 of the outer joint member 153 is inserted into theshaft section 163 of the hub wheel 152. In the shaft section 173, ascrew section 174 is formed at an end of a reverse cup-shaped sectionthereof. A spline section 175 is formed between this screw section 174and the cup-shaped section 157. A spline section 176 is formed on aninner circumferential surface (inner diameter surface) of the shaftsection 163 of the hub wheel 152. When this stem shaft 173 is insertedinto the shaft section 163 of the hub wheel 152, the spline section 175on the stem shaft 173 side and the spline section 176 on the hub wheel152 side are engaged.

A nut member 177 is screwed onto the screw section 174 of the stem shaft173 projecting from the shaft section 163. The hub wheel 152 and theouter joint member 153 are connected. An inner end surface (rearsurface) 178 of the nut member 177 and an outer end surface 179 of theshaft section 163 come into contact with each other and an end surface180 on a shaft section side of the cup-shaped section 157 and an outerend surface 181 of the inner ring 181 come into contact with each other.In other words, when the nut member 177 is tightened, the hub wheel 152is nipped by the nut member 177 and the cup-shaped section 157 throughan intermediation of the inner ring 167.

[Patent Document 1] JP 2004-340311 A

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Conventionally, as described above, the spline section 175 on the stemshaft 173 side and the spline section 176 on the hub wheel 152 side areengaged. Therefore, because it is necessary to apply spline machining toboth the stem shaft 173 side and the hub wheel 152 side, cost increases.When the stem shaft 173 is press-fit into the hub wheel 152, recessesand projections of the spline section 175 on the stem shaft 173 side andthe spline section 176 on the hub wheel 152 side need to be aligned. Ifthe stem shaft 173 is press-fit into the hub wheel 152 by aligning toothsurfaces thereof, recessed and projected teeth are likely to be damaged(torn). If the stem shaft 173 is press-fit into the hub wheel 152 byaligning the spline sections to a large diameter of the recessed andprojected teeth rather than aligning the tooth surfaces, a backlash in acircumferential direction tends to occur. If there is the backlash inthe circumferential direction in this way, transferability of rotationtorque is low and noise tends to occur. Therefore, when the stem shaft173 is press-fit into the hub wheel 152 by the spline fitting as in theprior art, it is difficult to solve both the damages to the recessed andprojected teeth and the backlash in the circumferential direction.

Further, it is necessary for the nut member 177 to be screwed on thescrew section 174 of the stem shaft 173 projecting from the shaftsection 163. Thus, the assembly work involves screw fastening operation,resulting in a rather poor workability. Further, the number ofcomponents is large, resulting in a rather poor componentcontrollability.

Even if adhesion of a male spline and a female spline is improved in thespline fitting to prevent the backlash in the circumferential directionfrom occurring, if driving torque acts, it is likely that relativedisplacement occurs in the male spline and the female spline. If suchrelative displacement occurs, fretting wear occurs. The splines arelikely to cause abrasion because of dust of the wear. Consequently, itis likely that a backlash occurs in a spline fitting region or stabletorque transmission cannot be performed.

In view of the above-mentioned problems, it is an object of the presentinvention to provide a bearing device for a wheel that can realizesuppression of a backlash in a circumferential direction and isexcellent in workability of connection of a hub wheel and an outer jointmember of a constant-velocity joint member, can perform stable torquetransmission over a long period of time and is excellent inmaintainability because separation of the hub wheel and the outer jointmember of the constant-velocity universal joint is possible, and canperform stable torque transmission over a long period of time.

Means for Solving the Problems

A first bearing device for a wheel according to the present inventionincludes an outer member having an inner circumference in which outerraceway surfaces in double rows are formed; an inner member that has, onan outer circumference thereof, inner raceway surfaces in double rowsopposed to the outer raceway surfaces and includes an inner ring and ahub wheel provided with flanges for attachment to a wheel; and rollingelements in double rows interposed between the outer raceway surfaces ofthe outer member and the inner raceway surfaces of the inner member, astem section of an outer joint member of a constant-velocity universaljoint being fit and coupled to an inner diameter of the hub wheel, inwhich: projections extending in an axial direction are provided in oneof a stem shaft of the outer joint member and an inner diameter surfaceof a hole of the hub wheel, the projections are press-fit into anotheralong the axial direction, and recesses that adhere to and fit on theprojections are formed on the another by this press fitting to configurethe recess-projection fitting structure in which entire fitting contactregions of the projections and the recesses adhere to each other; and anend on an inboard side of the hub wheel is caulked to an outer diameterside to form a caulking section, an inner ring of a roller bearingexternally fit in the hub wheel is fixed by this caulking section,preload is applied to the roller bearing, and the caulking section and aback surface of a mouth section of the outer joint member of theconstant-velocity universal joint opposed to this caulking section arebrought into contact with each other.

With the bearing device for a wheel according to the present invention,the bearing device for a wheel includes the recess-projection fittingstructure for integrating the hub wheel and the stem shaft of the outerjoint member of the constant-velocity universal joint fit and insertedinto the hole of the hub wheel. Therefore, a bolt and the like areunnecessary in coupling the stem shaft and the hub wheel. In therecess-projection fitting structure, entire fitting contact regions ofprojections and recesses are in close contact with each other.Therefore, in this fitting structure, a gap in which a backlash occursis not formed in a diameter direction and a circumferential direction.

Because the end of the hub wheel is caulked and preload is applied tothe roller bearing, it is unnecessary to apply preload with the mouthsection of the outer joint member.

The caulking section of the hub wheel and the back surface of the mouthsection of the outer joint member of the constant-velocity universaljoint opposed to this caulking section are brought into contact witheach other. Therefore, bending rigidity in a stem shaft direction isimproved. This bending rigidity is caused by secondary moment generatedduring a joint high actuation angle and axial load input from a tireside during turning.

It is preferable to provide a shaft slip-off preventing structure forregulating slip-off of the stem shaft from the hub wheel between thestem shaft of the outer joint member of the constant-velocity universaljoint and the inner diameter surface of the hub wheel. It is possible toprevent the outer joint member of the constant-velocity universal jointfrom slipping off from the hub wheel in the axial direction by providingthe shaft slip-off preventing structure.

The shaft slip-off preventing structure is a hook structure formed byplastically deforming a cylindrical section, which is provided at ashaft end of the stem shaft, outward in a diameter direction withswinging and caulking by a swinging caulking jig. Therefore, it ispossible to reduce caulking load during caulking compared with expansionof a diameter by pushing in the caulking jig in the axial directionwithout swinging the caulking jig.

The recess-projection fitting structure allows separation by applicationof drawing force in the axial direction. That is, if drawing force inthe axial direction is applied to the stem shaft of the outer jointmember, it is possible to remove the outer joint member from the hole ofthe hub wheel. After the stem shaft of the outer joint member is drawnout from the hole of the hub wheel, if the stem shaft of the outer jointmember is press-fit into the hole of the hub wheel again, it is possibleto configure the recess-projection fitting structure in which the entirefitting contact regions of the projections and the recesses are in closecontact with each other.

The hub wheel and the stem shaft of the outer joint member can be fixedthrough an intermediation of a bolt coupling means provided on a deviceaxis and having a screw hole and a bolt member screwed in this screwhole. Consequently, because the hub wheel and the stem shaft of theouter joint member are fixed through an intermediation of the boltcoupling means, slip-off in the axial direction of the stem shaft of theouter joint member from the hub wheel is regulated.

The bolt coupling means includes a shaft press-fitting guide structuresection of the outer joint member that guides the bolt member duringre-press fitting after the separation.

The bolt member has a screw section and a non-screw section, and theshaft press-fitting guide structure section has a bolt inserting holethrough which the non-screw section of the bolt member is inserted. Whena diameter difference between a hole diameter of the bolt inserting holeand a shaft diameter of the non-screw section of the bolt member isrepresented as Δd5 and a diameter difference between a stem shaft outerdiameter of the outer joint member in the recess-projection fittingstructure and a hub wheel inner diameter in the recess-projectionfitting structure is represented as Δd6, a relation between the diameterdifferences can be 0<Δd5<Δd6.

In other words, the diameter difference between the hole diameter of thebolt inserting hole and the shaft diameter of the non-screw section ofthe bolt member is set smaller than the diameter difference between thestem shaft outer diameter of the outer joint member and the hub wheelinner diameter in the recess-projection fitting structure. The boltinserting hole functions as a guide when the stem shaft of the outerjoint member is press-fit.

It is preferable to provide an inner wall for partitioning an inside ofthe hole of the hub wheel in the hole, and provide the bolt insertinghole in this inner wall. Rigidity of the shaft press-fitting guidestructure section is improved by this inner wall.

A seal material may be interposed at least one of between the caulkingsection of the hub wheel and an opposed surface of the outer jointmember opposed to the caulking section and between a bearing surface ofthe bolt member of the bolt coupling means and a receiving surface forreceiving this bearing surface.

It is preferable to set contact surface pressure between the caulkingsection of the hub wheel and the back surface of the mouth section isset to be equal to or lower than 100 MPa. When this contact surfacepressure exceeds 100 MPa, noise is likely to be caused. In other words,when torque load is large, a difference occurs in twisting amounts ofthe outer joint member of the constant-velocity universal joint and thehub wheel. Sudden slip occurs in the contact section of the outer jointmember of the constant-velocity universal joint and the hub wheelbecause of this difference, and noise occurs. On the other hand, whenthe contact surface pressure is equal to or lower than 100 MPa, it ispossible to prevent sudden slip from occurring and suppress occurrenceof noise.

The projections of the recess-projection fitting structure are providedin the stem shaft of the outer joint member of the constant-velocityuniversal joint, at least hardness of ends in the axial direction of theprojections is set higher than that of an inner diameter section of thehole of the hub wheel, and the stem shaft is press-fit into the hole ofthe hub wheel from an axial direction end side of the projections. Thus,recesses that adhere to and fit in the projections are formed on theinner diameter surface of the hole of the hub wheel by the projections,and the recess-projection fitting structure may be configured. Further,the projections of the recess-projection fitting structure are providedon the inner diameter surface of the hole of the hub wheel, at leasthardness of ends in the axial direction of the projections is set higherthan that of an outer diameter section of the stem shaft of the outerjoint member of the constant-velocity universal joint, and theprojections on a hub wheel side are press-fit into the stem shaft of theouter joint member from an axial direction end side of the projections.Thus, recesses that adhere to and fit in the projections are formed onan outer diameter surface of the stem shaft of the outer joint member bythe projections, and the recess-projection fitting structure may beconfigured.

Projecting direction intermediate regions of the projections arearranged on a recess forming surface before the formation of therecesses. When the projections are provided in the stem shaft of theouter joint member, a maximum diameter dimension of a circle connectingvertexes of the plural projections is set larger than an inner diameterdimension of the hub wheel shaft hole in which the recesses are formed.A diameter dimension of a circle connecting bottoms among theprojections is set smaller than an inner diameter dimension of the shaftfitting hole of the hub wheel. On the other hand, an outer diameterdimension of the stem shaft of the outer joint member is set larger thana minimum diameter dimension of a circle connecting vertexes of theplural projections provided in the hole of the hub wheel, and setsmaller than the diameter dimension of the circle connecting the bottomsamong the projections of the hub wheel hole.

It is preferable to set a circumferential direction thicknesses of theprojecting direction intermediate regions of the projections smallerthan a circumferential direction dimension in positions corresponding tothe intermediate regions among the projections adjacent to one anotherin the circumferential direction. By setting the circumferentialdirection thicknesses in this way, it is possible to set a sum of thecircumferential direction thicknesses of the projecting directionintermediate regions of the projections smaller than a sum ofcircumferential direction thicknesses in positions corresponding to theintermediate regions in the projections on the other side that fit inamong the projections adjacent to one another in the circumferentialdirection.

It is preferable to arrange the recess-projection fitting structurewhile avoiding a position right below the raceway surface of the rollerbearing. In other words, if the shaft section is press-fit into the holeof the hub wheel, the hub wheel expands. Hoop stress is generated on theraceway surface of the roller bearing by this expansion. The hoop stressmeans force for expanding a diameter in the outer diameter direction.Therefore, when the hoop stress is generated on the bearing racewaysurface, there is a fear that the hoop stress reduces rolling fatiguelife and causes a crack. Therefor, it is possible to suppress generationof the hoop stress on the bearing raceway surface by arranging therecess-projection fitting structure while avoiding a position rightbelow the raceway surface of the roller bearing.

It is preferable to provide a pocket section that stores an extrudedportion caused by the recess formation by the press fitting. It ispossible to provide the pocket section that stores the extruded portioncaused by the recess formation by the press fitting and provide thepocket section on the inner diameter surface of the hole of the hubwheel. The extruded portion is equivalent to a volume of a material inthe recesses in which the recess fitting regions of the projection arefit in. The extruded portion includes the material extruded from therecesses to be formed, the material cut for forming the recesses, or thematerial extruded and cut. It is preferable to provide the pocketsection for storing the extruded portion on a press fitting start endside of the projections of the stem shaft and provide a collar sectionfor centering with the hole of the hub wheel on an axial directionopposite projection side of this pocket section.

Effect of the Invention

The bearing device for a wheel according to the present inventionincludes the recess-projection fitting structure for integrating the hubwheel and the stem shaft of the outer joint member of theconstant-velocity universal joint fit and inserted into the hole of thehub wheel. Therefore, it is possible to eliminate a backlash in thecircumferential direction of the recess-projection fitting structuresection.

The caulking section and the back surface of the mouth section of theouter joint member are brought into contact with each other, wherebybending rigidity in the stem shaft direction is improved, the stem shaftbecomes robust against bending, and a high-quality product excellent indurability is obtained. Moreover, positioning during press fitting canbe realized by this contact. Consequently, dimension accuracy of thisbearing device for a wheel is stabilized, it is possible to securestable length as axial direction length of the recess-projection fittingstructure disposed along the axial direction and realize improvement oftorque transmission performance. Further, a seal structure can beconfigured by this contact. It is possible to prevent intrusion offoreign matters into the recess-projection fitting structure from thecaulking section side of this hub wheel. The recess-projection fittingstructure can maintain a stable fit state over a long period of time.

Because the end of the hub wheel is caulked and preload is applied tothe roller bearing, it is unnecessary to apply preload with the mouthsection of the outer joint member. Therefore, it is possible topress-fit the stem shaft of the outer joint member without taking intoaccount preload and realize improvement of connectability(assemblability) of the hub wheel and the outer joint member.

With the shaft slip-off preventing structure, it is possible toeffectively prevent the stem shaft of the outer joint member fromslipping off in the axial direction from the hole of the hub wheel.Consequently, it is possible to maintain a stable connected state andrealize improvement of a quality of the bearing device for a wheel.Therefore, nut fastening work is unnecessary when the stem shaft and thehub wheel are coupled. Therefore, it is possible to easily performassembly work, realize a reduction in cost in the assembly work, andrealize a reduction in weight.

It is possible to remove the outer joint member from the hole of the hubwheel by applying drawing force in the axial direction to the stem shaftof the outer joint member. Therefore, it is possible to realizeimprovement of workability (maintainability) of repairing and inspectionof components. Moreover, by press-fitting the stem shaft of the outerjoint member into the hole of the hub wheel again after repairing andinspection of the components, it is possible to configure therecess-projection fitting structure in which the entire fitting contactregions of the projections and the recesses are in close contact witheach other. Therefore, it is possible to configure the bearing devicefor a wheel, which can perform stable torque transmission, again.

In the bearing device for a wheel in which the hub wheel and theconstant-velocity universal joint are fixed through an intermediation ofthe bolt coupling means, slip-off in the axial direction of the stemshaft of the outer joint member from the hub wheel is regulated. It ispossible to maintain a stable connected state.

Because the shaft slip-off preventing structure is a hook structureformed by plastically deforming the cylindrical section outward in thediameter direction, screw fastening in the prior art can be omitted.Therefore, it is unnecessary to form the screw section projecting fromthe hole of the hub wheel in the shaft section. It is possible torealize a reduction in weight, omit screw fastening work, and realizeimprovement of assembly workability. Moreover, caulking load duringcaulking may be relatively small. It is possible to increase thethickness of the caulking section and surely bring the inner diametersurface of the hub wheel and the outer diameter surface of the caulkingsection into contact with each other. Consequently, it is possible toprovide a more robust slip-off preventing mechanism (structure).Further, because such a robust slip-off preventing mechanism (structure)is provided, bending rigidity of the shaft section is improved and theshaft section becomes robust against bending. If the caulking loadduring caulking can be reduced, it is possible to prevent deformation ofa region that receives load (a load receiving section of the outer jointmember of the constant-velocity universal joint, for example, a stepsurface provided on the outer diameter surface of the outer jointmember, an opening side end surface of the outer joint member, etc.).

Because the diameter difference between the hole diameter of the boltinserting hole and the shaft diameter of the non-screw section of thebolt member is set smaller than the diameter difference between the stemshaft outer diameter of the outer joint member and the hub wheel innerdiameter in the recess-projection fitting structure, the bolt insertinghole functions as a guide when the stem shaft of the outer joint memberis press-fit. It is possible to perform more stable re-press fitting.

The rigidity of the shaft press-fit guide structure section is improvedand press fitting of the stem shaft of the outer joint member is morestabilized by the inner wall of the hole of the hub wheel.

If a seal material is interposed between the caulking section of the hubwheel and the opposed surface of the outer joint member opposed to thecaulking section, it is possible to prevent intrusion of rainwater,foreign matters, and the like into the recess-projection fittingstructure from a space between the caulking section and the opposedsurface. If a seal material is interposed between a bearing surface ofthe bolt shaft of the bolt coupling means and a receiving surface thatreceives the bearing surface, it is possible to prevent intrusion ofrainwater, foreign matters, and the like into the recess-projectionfitting structure from a space between the bearing surface and thereceiving surface.

If contact surface pressure between the caulking section of the hubwheel and the back surface of the mouth section is equal to or lowerthan 100 MPa, it is possible to prevent sudden slip from occurring andsuppress occurrence of noise. Consequently, it is possible to configurea silent bearing device for a wheel.

The projections of the recess-processing fitting structure are providedin the stem shaft of the outer joint member of the constant-velocityuniversal joint, the hardness of the axial direction ends of theprojections is set higher than that of the inner diameter section of thehole of the hub wheel, and the stem shaft is press-fit in the hole ofthe hub wheel from the axial direction end side. As a result, it ispossible to increase the hardness on the stem shaft side and improve therigidity of the stem shaft. The projections of the recess-projectionfitting structure are provided on the inner diameter surface of the holeof the hub wheel, the hardness of the axial direction ends of theprojections is set higher than that of the outer diameter section of thestem shaft of the outer joint member of the constant-velocity universaljoint, and the projections on the hub wheel side are press-fit in thestem shaft of the outer joint member from the axial direction end sidethereof. As a result, it is unnecessary to perform hardness treatment(heat treatment) on the stem shaft side. Therefore, the outer jointmember of the constant-velocity joint is excellent in productivity.

By setting the circumferential direction thickness of the projectingdirection intermediate region of the projections smaller than adimension in positions corresponding to the intermediate regions amongthe projections adjacent to one another in the circumferentialdirection, it is possible to increase the circumferential directionthickness of the projecting direction intermediate regions of theprojections on the side in which the recesses are formed (projectionsamong the formed recesses). Therefore, it is possible to increase ashearing area of the projections on the opposite side (projectionshaving low hardness among the recesses because the recesses are formed)and secure torsion strength. Moreover, because tooth thickness of theprojections on the high hardness side is small, it is possible to reducepress-fitting load and realize improvement of press-fitting properties.

Generation of hoop stress on the bearing raceway surface is suppressedby arranging the recess-projection fitting structure while avoiding aposition right below the raceway surface of the roller bearing.Consequently, it is possible to prevent occurrence of a deficiency ofthe bearing such as a reduction in rolling fatigue life, occurrence of acrack, and stress corrosion crack.

By providing the pocket section for storing the extruded portion causedby recess formation by the press fitting, it is possible to hold(maintain) the extruded portion in this pocket. The extruded portiondoes not enter the inside of the vehicle and the like on the outside ofthe device. In other words, it is possible to keep the extruded portionstored in the pocket section, it is unnecessary to perform removalprocessing for the extruded portion, and it is possible to realize areduction in assembly work man-hour and realize improvement of assemblyworkability and cost reduction.

By providing the collar section for centering with the hole of the hubwheel on the opposite projection side in the axial direction of thepocket section, ejection of the extruded portion in the pocket sectionto the collar section side is eliminated. The extruded portion is morestably stored. Moreover, because the collar section is used forcentering, it is possible to press-fit the stem shaft into the hub wheelwhile preventing decentering. Therefore, it is possible to highlyaccurately connect the outer joint member and the hub wheel and performstable torque transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged sectional view of a bearing device for a wheelillustrating a first embodiment of the present invention.

FIG. 2A is an enlarged sectional view of a recess-projection fittingstructure of the bearing device for a wheel.

FIG. 2B is an enlarged view of an X section illustrated in FIG. 2A.

FIG. 3 is a main part enlarged sectional view of the bearing device fora wheel.

FIG. 4 is a main part enlarged sectional view of the recess-projectionfitting structure of the bearing device for a wheel.

FIG. 5 is a sectional view before assembly of the bearing device for awheel.

FIG. 6 is a sectional view illustrating a process for assembling thebearing device for a wheel using a jig.

FIG. 7 is a sectional view illustrating the process for assembling thebearing device for a wheel using the jig.

FIG. 8 is a sectional view illustrating the process for assembling thebearing device for a wheel using the jig.

FIG. 9 is a sectional view illustrating a method of press-fitting asingle outer ring into a hub wheel.

FIG. 10 is a sectional view illustrating a method of press-fitting anouter ring, an inner ring, a ball, and a cage into the hub wheel in anassembled state.

FIG. 11 is a sectional view illustrating a process of assembling thebearing device for a wheel using another jig.

FIG. 12 is a sectional view illustrating the process of assembling thebearing device for a wheel using another jig.

FIG. 13 is a longitudinal sectional view of a bearing device for a wheelillustrating a second embodiment of the present invention.

FIG. 14 is a longitudinal sectional view of a bearing device for a wheelillustrating a third embodiment of the present invention.

FIG. 15 is a sectional view illustrating a method of assembling thebearing device for a wheel illustrated in FIG. 14.

FIG. 16 is a sectional view illustrating the method of assembling thebearing device for a wheel illustrated in FIG. 14.

FIG. 17 is a longitudinal sectional view of a bearing device for a wheelillustrating a fourth embodiment of the present invention.

FIG. 18 is a sectional view illustrating a method of assembling thebearing device for a wheel illustrated in FIG. 17.

FIG. 19 is a sectional view illustrating the method of assembling thebearing device for a wheel illustrated in FIG. 17.

FIG. 20A is an end surface view of an outer collar-like locking sectionover an entire circumference, illustrating an end surface of a stemshaft of an outer ring of the bearing device for a wheel illustrated inFIG. 17.

FIG. 20B is an end surface view of outer collar-like locking sectionsdisposed at a predetermined pitch along a circumferential direction,illustrating the end surface of the stem shaft of the outer ring of thebearing device for a wheel illustrated in FIG. 17.

FIG. 21 is a longitudinal sectional view of a bearing device for a wheelillustrating a fifth embodiment of the present invention.

FIG. 22 is a main part sectional view of a bearing device for a wheelillustrating a sixth embodiment of the present invention.

FIG. 23 is a main part sectional view of a bearing device for a wheelillustrating a seventh embodiment of the present invention.

FIG. 24 is a main part sectional view of a bearing device for a wheelillustrating an eighth embodiment of the present invention.

FIG. 25 is a main part enlarged sectional view of the bearing device fora wheel illustrated in FIG. 24.

FIG. 26 is a main part sectional view of a bearing device for a wheelillustrating a ninth embodiment of the present invention.

FIG. 27 is a main part enlarged longitudinal sectional view of thebearing device for a wheel illustrated in FIG. 26.

FIG. 28A is a sectional view taken along the W-W line in FIG. 26,illustrating a shaft press-fitting structure of the bearing device for awheel illustrated in FIG. 26.

FIG. 28B is an enlarged sectional view illustrating a first modificationof the shaft press-fitting structure.

FIG. 28C is an enlarged sectional view illustrating a secondmodification of the shaft press-fitting structure.

FIG. 29 is a main part enlarged view of the bearing device for a wheelillustrated in FIG. 26.

FIG. 30 is a sectional view before assembly of the bearing device for awheel illustrated in FIG. 26.

FIG. 31 is a sectional view illustrating a method of separating thebearing device for a wheel illustrated in FIG. 26.

FIG. 32 is a sectional view before reassembly of the bearing device fora wheel illustrated in FIG. 26.

FIG. 33 is a sectional view illustrating a method of reassembling thebearing device for a wheel illustrated in FIG. 26.

FIG. 34A is a sectional view in a state immediately beforepress-fitting, illustrating a method of re-press-fitting the bearingdevice for a wheel illustrated in FIG. 26.

FIG. 34B is a sectional view during press fitting, illustrating themethod of re-press-fitting the bearing device for a wheel illustrated inFIG. 26.

FIG. 34C is a sectional view of a press fitting completion state,illustrating the method of re-press-fitting the bearing device for awheel illustrated in FIG. 26.

FIG. 35A is a sectional view illustrating a first modification of therecess-projection fitting structure.

FIG. 35B is a sectional view illustrating a second modification of therecess-projection fitting structure.

FIG. 36A is a sectional view of a third modification of the shaftpress-fitting structure.

FIG. 36B is a sectional view of a fourth modification of the shaftpress-fitting structure.

FIG. 36C is a sectional view of a fifth modification of the shaftpress-fitting structure.

FIG. 37 is a sectional view illustrating a tenth embodiment of thepresent invention.

FIG. 38A is a cross sectional view of a third modification of therecess-projection fitting structure.

FIG. 38B is an enlarged view of a Y section illustrated in FIG. 38A.

FIG. 39 is a sectional view of a conventional bearing device for awheel.

FIG. 40 is a sectional view of a seal material interposed between abearing surface of a bolt member and an inner wall.

FIG. 41 is a sectional view of a seal material interposed between an endsurface of a caulking section and a bottom back surface of a mouthsection.

DESCRIPTION OF SYMBOLS Detailed Description of the Invention

Embodiments of the present invention are described below with referenceto FIGS. 1 to 41. A bearing device for a wheel according to a firstembodiment is illustrated in FIG. 1. In this bearing device for a wheel,a hub wheel 1, roller bearings 2 in double rows, and a constant-velocityuniversal joint 3 are integrated and the hub wheel 1 and a stem shaft 12of an outer joint member of the constant-velocity universal joint 3 fitand inserted into a hole 22 of the hub wheel 1 are coupled through anintermediation of a recess-projection fitting structure M.

The constant-velocity universal joint 3 mainly includes an outer ring 5as an outer joint member, an inner ring 6 as an inner joint memberarranged on the inner side of the outer ring 5, plural balls 7 providedbetween the outer ring 5 and the inner ring 6 to transmit torque, and acage 8 provided between the outer ring 5 and the inner ring 6 andadapted to retain the balls 7. An end section 10 a of a shaft 10 ispress-fitted into a shaft hole inner diameter 6 a of the inner ring 6 toeffect spline fitting, whereby connection with the shaft 10 is effectedso as to allow torque transmission. A stop ring 9 for preventing shaftslipping-off is fit in the end section 10 a of the shaft 10.

The outer ring 5 includes a mouth section 11 and a stem section (shaftsection) 12, and the mouth section 11 is formed in a cup-like shape openat its one end. In an inner spherical surface 13 thereof, there areformed plural axially extending guiding grooves (track grooves) 14 atequal circumferential intervals. The inner ring 6 has in an outerspherical surface 15 thereof plural axially extending guiding grooves(track grooves) 16 formed at equal circumferential intervals.

The track grooves 14 of the outer ring 5 and the track grooves 16 of theinner ring 6 are paired with each other, and one ball 7 as a torquetransmission element (torque transmission member) is incorporated into atrack formed by each pair of track grooves 14, 16 so as to be capable ofrolling. The balls 7 are provided between the track grooves 14 of theouter ring 5 and the track grooves 16 of the inner ring 6 to transmittorque. The cage 8 is slidably provided between the outer ring 5 and theinner ring 6, with an outer spherical surface thereof coming in contactwith the inner spherical surface 13 of the outer ring 5 and an innerspherical surface thereof coming in contact with the outer sphericalsurface 15 of the inner ring 6. While in this example theconstant-velocity universal joint is of the undercut free type, in whicheach track grooves 14, 16 has a linear straight section provided to agroove bottom. It is also possible to adopt a constant-velocityuniversal joint of some other type such as the zepper type in which thelinear straight section is not provided to the bottom.

Further, the opening of the mouth section 11 is stopped by a boot 18.The boot 18 includes a large diameter section 18 a, a small diametersection 18 b, and a bellows section 18 c connecting the large diametersection 18 a and the small diameter section 18 b. The large diametersection 18 a is fitted onto the opening of the mouth section 11, and isfastened in this state by a boot band 19 a. Further, the small diametersection 18 b is fitted onto a boot attachment section 10 b of the shaft10, and is fastened in this state by a boot band 19 b.

The hub wheel 1 includes, as illustrated in FIG. 1 and FIG. 5, acylindrical section 20, and a flange 21 provided at the out board sideend section of the cylindrical section 20. A hole 22 of the cylindricalsection 20 includes a shaft section fitting hole 22 a, a tapered hole 22b on the out board side, and a large diameter section 22 c on thein-board side. Between the shaft section fitting hole 22 a and the largediameter section 22 c, there is provided a taper section (tapered hole)22 d. This taper section 22 d is reduced in diameter along apress-fitting direction in coupling the hub wheel 1 and the stem shaft12 of the outer ring 5. A tilt angle θ1 of the taper section 22 d is setto, for example, 15° to 75°. The outboard side is an outer side of thevehicle in a state in which the bearing device is attached to thevehicle and the inboard side is an inner side of the vehicle in thestate in which the bearing device is attached to the vehicle.

The roller bearing 2 includes an inner ring 24 fit in a step section 23provided on the inboard side of the cylinder section 20 of the hub wheel1 and an outer member 25 externally fit from the cylinder section 20 tothe inner ring 24 of the hub wheel 1. In the outer member 25, outerraceway surfaces (outer races) 26 and 27 in two rows are provided on aninner circumference thereof. The first outer raceway surface 26 and afirst inner raceway surface (inner race) 28 provided on an outercircumference of the shaft section of the hub wheel 1 are opposed toeach other. The second outer raceway surface 27 and a second innerraceway surface (inner race) 29 provided on an outer circumferentialsurface of the inner ring 24 are opposed to each other. Balls as rollingelements 30 are interposed between the first outer raceway surface 26and the first inner raceway surface 28 and between the second outerraceway surface 27 and the second inner raceway surface 29. Therefore,in this bearing device for a wheel, the hub wheel 1 and the inner ring24 configure an inner member 39 of the roller bearing 2. Seal members S1and S2 are inserted in both openings of the outer member 25.

A knuckle 34 (see FIG. 26, etc.) extending from a suspension system fora vehicle body not shown in the figure is attached to the outer ring asthe outer member 25. An entire outer surface of the outer member 25 isformed as a cylindrical surface. This cylindrical surface is set as apress-fitting surface 25 a in which the knuckle 34 is press-fit.Consequently, the outer member 25 can be press-fit into a cylindricalinner diameter surface of the knuckle. In this case, it is desirable toset to regulate, with a tightening margin between the knucklepress-fitting surface 25 a and the knuckle inner diameter surface,relative shift in an axial direction and a circumferential direction ofthe knuckle 34 and the outer member 25. For example, when mating surfacepressure×mating area between the outer member 25 and the knuckle 34 ismating load, a value obtained by dividing this mating load withequivalent radial load of this bearing for a wheel is set as a creepoccurrence limit coefficient. A design specification for the outermember 25, i.e., a fitting margin between the outer member 25 and theknuckle is set by taking into account this creep occurrence limitcoefficient in advance.

Therefore, it is possible to prevent slip-off in the axial direction andcreep in the circumferential direction of the outer member 25 with thetightening margin between the knuckle press-fitting surface 25 a of theouter member 25 and the knuckle inner diameter surface of the knuckle34. The creep means that the bearing slightly moves in thecircumferential direction because of insufficiency of the mating margin,machining accuracy failure of the fitting surface, or the like and themating surface changes to a mirror surface and, in some case, thefitting surface involves score, and seizure or adhesion occurs. Asillustrated in FIG. 26 and the like, it is preferable to providecircumferential direction grooves in the knuckle press-fitting surface25 a of the outer member 25 and an inner diameter surface 34 a of theknuckle 34, respectively, and a lock ring 61 for slip-off prevention isinserted between those circumferential direction grooves.

In this case, the end on the inboard side of the hub wheel 1 is caulkedand the inner ring 24 is pressed to the outboard side by the caulkingsection 31, whereby preload is applied to this bearing 2. Consequently,the inner ring 24 can be fastened to the hub wheel 1. An end surface 24a on the inboard side of the inner ring 24 is pressed to the outboardside along the axial direction by the caulking section 31. An endsurface 24 b on the outboard side of the inner ring 24 comes intocontact or press-contact with the end surface 23 a of the step section23. A bolt inserting hole 32 is provided in the flange 21 of the hubwheel 1. A hub bolt 33 for fixing a wheel and a brake rotor to thisflange 21 are inserted into this bolt inserting hole 32.

As illustrated in FIG. 2, the recess-projection fitting structure M isformed, for example, of axially extending projections 35 provided to thestem shaft 12, and recesses 36 formed in the inner diameter surface ofthe hole section 22 of the hub wheel 1 (inner diameter surface 37 ofshaft section fitting hole 22 a in this case). The entire regions of thefitting contact regions 38 of the projections 35 and the recesses 36 ofthe hub wheel 1 fit in the projections 35 are held in close contact.Plural projections 35 are arranged at a predetermined circumferentialpitch on the outer peripheral surface of the opposite mouse side of thestem shaft 12, and plural recesses 36 to be fit in the projections 35are formed circumferentially in the inner diameter surface 37 of theshaft section fitting hole 22 a of the hole 22 of the hub wheel 1. Thatis, over the circumferential entire periphery, the projections 35 andthe recesses 36 fit-engaged thereto are tightly fit in each other.

In this case, the respective projections 35 are formed in a triangularshape (ridge shape) having a vertex of a projected R shape in section.Fitting contact regions (recess fitting regions) 38 of the projections35 are ranges A illustrated in FIG. 2B and ranges from halfway sectionsof the ridges in section to the tops of the ridges. A gap 40 is formedfurther on an inner diameter side than an inner diameter surface 37 ofthe hub wheel 1 between the projections 35 adjacent to each other in thecircumferential direction.

In this way, the hub wheel 1 and the stem shaft 12 of the outer ring 5of the constant-velocity universal joint 3 can be connected through anintermediation of the recess-projection fitting structure M. Inconnecting the hub wheel 1 and the stem shaft 12, because the end on theinboard side of the hub wheel 1 is caulked and preload is applied to theroller bearing 2 by the caulking section 31 as described above, it isunnecessary to apply preload to the inner ring 24 in the mouth section11 of the outer ring 5. However, in the present invention, the end ofthe hub wheel 1 (in this case, an outer end surface 31 a of the caulkingsection 31) and an opposed surface of the outer ring 5 opposed to theend of the hub wheel 1 (back surface 11 a of the mouth section 11) arebrought into contact with each other. Contact surface pressure in thiscase is set to be equal to or smaller than 100 MPa.

Incidentally, the shaft slip-off preventing structure M1 is providedbetween the end of the stem shaft 12 of the outer ring 5 and the innerdiameter surface 37 of the hub wheel 1. This shaft slip-off preventingstructure M1 includes an expanded-diameter caulking section (taperedlocking piece) 65 that extends from the end of the stem shaft 12 of theouter ring 5 to the outboard side and locks to a tapered hole 22 b. Inother words, the expanded-diameter caulking section 65 includes aring-like member that increases in diameter from the inboard side to theoutboard side. At least a part of an outer circumferential surface 65 athereof comes into press-contact or contact with the tapered hole 22 b.

In this bearing device for a wheel, foreign-matter intrusion preventingmeans W for preventing intrusion of foreign matters into therecess-projection fitting structure M are respectively provided furtheron the inboard side (the inner side of the vehicle in the state in whichthe bearing device is attached to be vehicle) than the recess-projectionfitting structure M and further on the outboard side (the outer side ofthe vehicle in the state in which the bearing device is attached to thevehicle) than the recess-projection fitting structure M.

The out board side foreign-matter intrusion prevention means W2 can beformed of a seal material (not shown) provided between the taperedlocking piece 65 described above constituting an engagement section andthe inner diameter surface of the tapered hole 22 b. In this case, aseal material is applied to the tapered locking piece 65. That is, thereis applied a seal material (seal agent) selected from among variousresins curable after the application and capable of exerting sealingproperty between the tapered locking piece 65 and the inner diametersurface of the tapered hole 22 b. Note that, as this seal material,there is selected one that does not deteriorate in the atmosphere inwhich this bearing device for a wheel is used.

The foreign-matter intrusion preventing means W1 on the inboard side canbe configured by bringing the outer end surface 31 a of the caulkingsection 31 of the hub wheel 1 and the back surface 11 a of the mouthsection 11 into contact with each other. A seal material (seal agent)may be applied to at least one of the outer end surface 31 a and theback surface 11 a.

It is also possible to provide a seal material in the fitting contactregion 38 between the projections 35 and the recesses 36, and in a gap40, thereby forming a foreign-matter intrusion prevention means W (W3).In this case, there is applied to the surfaces of the projections 35 aseal material (seal agent) selected from among various resins curableafter the application and capable of exerting sealing property in thefitting contact region 38.

When this bearing device for a wheel is assembled, as described later,the recesses 36 are formed by the projections 35 by press-fitting thestem shaft 12 of the outer ring 5 into the hub wheel 1. When the stemshaft 12 is press-fit into the hub wheel 1, a material is extruded fromthe recesses 36 formed by the projections 35 and an extruded portion 45(see FIG. 3) is formed. The extruded portion 45 is equivalent to avolume of the material of the recesses 36 in which recess fittingregions of the projections 35 are fit in. The extruded portion 45includes the material extruded from the recesses 36 to be formed, thematerial cut for forming the recesses 36, or the material extruded andcut. Therefore, in the bearing device for a wheel illustrated in FIG. 1and the like, a pocket section 50 for storing the extruded portion 45 isprovided to the stem shaft 12.

The pocket section 50 is formed by providing a circumferential directiongroove 51 at a shaft edge of a spline 41 of the stem shaft 12. Theexpanded-diameter caulking section (tapered locking piece) 65configuring the shaft slip-off preventing structure M1 is formed furtheron an opposite spline side than the circumferential direction groove 51.

A method of fitting the recess-projection fitting structure M isdescribed. In this case, as illustrated in FIG. 5, thermosettingtreatment is applied to an outer diameter section of the stem shaft 12of the outer ring 5 of the constant-velocity universal joint 3. Thespline 41 including projections 41 a and recesses 41 b along the axialdirection is formed in this hardened layer H. Therefore, the projections41 a of the spline 41 are hardened and changes to the projections 35 ofthe recess-projection fitting structure M. A range of the hardened layerH in this embodiment is, as indicated by a cross hatching section, froman outer edge of the spline 41 to a part of a bottom wall of the mouthsection 11 of the outer ring 5. As this thermosetting treatment, variouskinds of heat treatment such as induction hardening and carburizing andquenching can be adopted. The induction hardening is a hardening methodemploying the principle of inserting a section necessary for hardeninginto a coil through which a high-frequency current flows, generatingJoule heat with an electromagnetic induction action, and heating aconductive substance. The carburizing and quenching is a method ofcausing carbon to intrude/spread from the surface of a low carbonmaterial and performing hardening after that. A hardened layer H1 by theinduction hardening is formed on the outer diameter side of the hubwheel 1 and the inner diameter side of the hub wheel is left in anunhardened state. A range of the hardened layer H1 in this embodimentis, as indicated by a cross hatching section, from a base section of theflange 21 to near the caulking section of the step section 23 in whichthe inner ring 24 fits.

If the induction hardening is performed, the surface can be hard andhardness of a material in the inside can be kept. Therefore, the innerdiameter side of the hub wheel 1 can be maintained in the unhardenedstate. The inner diameter surface 37 side of the hole 22 of the hubwheel 1 is an unhardened section not subjected to the thermosettingtreatment (in an unhardened state). A hardness difference between thehardened layer H of the stem shaft 12 of the outer ring 5 and theunhardened section of the hub wheel 1 is set to be equal to or largerthan 20 points in HRC. Specifically, the hardness of the hardened layerH is set to about 50 HRC to 65 HRC and the hardness of the unhardenedsection is set to about 10 HRC to 30 HRC.

In this case, a projecting direction intermediate region of theprojections 35 corresponds to a position of a recess forming surfacebefore recess formation (in this case, the inner diameter surface 37 ofthe hole 22 of the hub wheel 1). That is, as illustrated in FIG. 4, aninner diameter dimension D of the inner diameter surface 37 of the hole22 is set smaller than a maximum outer diameter of the projections 35,i.e., a maximum diameter dimension (circumscribed circle) D1 of a circleconnecting vertexes of the projections 35 as the projections 41 a of thespline 41 and is set larger than an outer diameter dimension of a shaftouter diameter surface among the projections, i.e., a maximum diameterdimension D2 (see FIG. 5) of a circle connecting bottoms of the recesses41 b of the spline 41. In other words, the dimensions are set in arelation of D2<D<D1.

The spline 41 can be formed by various machining methods such ascomponent rolling, cutting, pressing, and drawing, which are publiclyknown and used conventional means. As the thermosetting treatment,various kinds of heat treatment such as induction hardening andcarburizing and quenching can be adopted.

As illustrated in FIG. 5, before the stem shaft 12 of the outer ring 5is press-fit into the hole 22 of the hub wheel 1, a cylindrical section66 for configuring the expanded-diameter caulking section 65 isprojected from an outer circumferential edge of the end surface 12 a ofthe stem shaft 12 along the axial direction. An outer diameter D4 of thecylindrical section 66 is set smaller than an inner diameter dimension Dof a fitting hole 22 a of the hole 22. As described later, thiscylindrical section 66 functions as a guide section for centering duringpress fitting of the hub wheel 1 of the stem shaft 12 into the hole 22.Further, an inner diameter D3 of a large diameter section 22 c of thehub wheel 1 is set larger than the maximum diameter dimension(circumscribed circle diameter) D1. If the outer diameter D4 of thecylindrical section 66 is the same as or larger than a hole diameter ofthe fitting hole 22 a, the cylindrical section 66 itself is press-fitinto the fitting hole 22 a. When the cylindrical section 66 ispress-fit, if the cylindrical section 66 is decentered, the projections35 of the recess-projection fitting structure M are press-fit in thisstate. The shaft section 12 and the hub wheel 1 are connected in a statein which the axis of the stem shaft 12 and the axis of the hub wheel 1are not aligned. Further, if the outer diameter D4 of the cylindricalsection 66 is too smaller than the hole diameter of the fitting hole 22a, the cylindrical section 66 does not function as the guide section forcentering. Therefore, it is preferable to set a very small gap betweenthe outer diameter surface of the cylindrical section 66 and the innerdiameter surface of the fitting hole 22 a of the hole 22 to about 0.01mm to 0.2 mm.

The stem shaft 12 of the outer ring 5 is inserted (press-fit) into thehub rig 1 in a state in which the axis of the hub wheel 1 and the axisof the outer ring 5 of the constant-velocity universal joint arealigned. A seal material is applied to the surface of the projection 35in advance. When the stem shaft 12 is inserted, because the tapersection 22 d the decreases in diameter along a press-fitting directionis formed in the hole 22 of the hub wheel 1, this taper section 22 d canform a guide at the start of press fitting. The diameter dimension D ofthe inner diameter surface 37 of the hole 22, the maximum diameterdimension D1 of the projections 35, and the outer diameter dimension(diameter dimension) D2 of the recess bottoms of the spline 41 are inthe relation described above. Moreover, the hardness of the projections35 is larger than the hardness of the inner diameter surface 37 of thehole 22 by 20 points or more. Therefore, if the shaft 10 is press-fitinto the hole 22 of the inner ring 6, the projections 35 bite in theinner diameter surface 37. The projections 35 form the recesses 36, inwhich the projections 35 fit, along the axial direction.

Because the shaft 10 is press-fit in the hole 22 in this away, asillustrated in FIG. 3, the extruded portion 45 to be formed is stored inthe pocket section 50 while curling. In other words, a part of thematerial scraped off or extruded from the inner diameter surface of thehole 22 enters the pocket section 50.

According to the press fitting, as illustrated in FIG. 2, the entirefitting contact regions 38 of the projections 35 at the end of the stemshaft 12 and the recesses 36 fit therein adhere to each other. In otherwords, a shape of the projections 35 is transferred onto a recessformation surface on the opposite side (in this case, the inner diametersurface 37 of the hole 22). When the shape is transferred, because theprojections 35 bite in the inner diameter surface 37 of the hole 22, thehole 22 is slightly expanded in diameter and allows movement in theaxial direction of the projections 35. If the movement in the axialdirection stops, the hole 22 decreases in diameter to return to theoriginal diameter. In other words, the hub wheel 1 is elasticallydeformed in the diameter direction when the projections 35 arepress-fit, and preload equivalent to this elastic deformation is appliedto a tooth surface of the projections 35 (surface of the recess fittingregion). Therefore, it is possible to surely form the recess-projectionfitting structure M in which the entire recess fitting regions of theprojections 35 adhere to the recesses 36 corresponding thereto.

That is, a female spline 42 adhering to the spline (male spline) 41 onthe stem shaft 12 side is formed on the inner diameter surface of thehole 22 of the hub wheel 1 by the male spline 41. Further, a spacebetween the fitting contact regions 38 of the projections 35 and therecesses 36 are sealed by the seal material applied to the surface ofthe projections 35.

The recess-projection fitting structure M is configured as describedabove. The recess-projection fitting structure M in this case isarranged avoiding positions right below the raceway surfaces 26, 27, 28,and 29 of the roller bearing 2. Positions avoiding the positions rightbelow the raceway surfaces 26, 27, 28, and 29 are positions notcorresponding to ball contacting positions of the raceway surfaces 26,27, 28, and 29 in the diameter direction.

In this recess-projection fitting structure M, as illustrated in FIG. 4,when a diameter difference (D1−D) between the maximum diameter dimensionD1 of the stem shaft 12 and the inner diameter dimension D of thefitting hole 22 a of the hole 22 of the hub wheel 1 is represented asΔd, the height of the projections 35 provided on the outer diametersurface of the stem shaft 12 is represented as h, and a ratio of thediameter difference and the height is represented as Δd/2h, a relationamong the diameter difference, the height, and the ratio is0.3<Δd/2h<0.86. Consequently, the projecting direction intermediateregions (height direction intermediate regions) of the projections 35are surely arranged on the recess formation surface before recessformation. Therefore, the projections 35 bite in the recess formationsurface during press fitting and the recesses 36 can be surely formed.

When the stem shaft 12 of the outer ring 5 is press-fit in the hole 22of the hub wheel 1, a step surface G is provided on the outer diametersurface of the mouth section 11 of the outer ring 5 as illustrated inFIG. 1 and the like. A press-fitting jig K only has to be engaged withthis step surface G to apply press-fitting load (axial direction load)from this press-fitting jig K to the step surface G. Note that the stepsurface G can be formed by a circumferential direction groove providedon the outer diameter surface of the mouth section 11.

The press-fitting jig K can be formed by a ring-like member 47 made of,for example, a split mold. In other words, the ring-like member 47includes plural (at least two) segments 47 a and is formed in a ringshape by combining the segments 47 a. The ring-like member 47 formed bycombining the segments 47 a in the ring shape includes a main bodyannular section 57, a taper section 58 connected to this main bodyannular section 57, and an inner collar section 59 projecting from thistaper section 58 to the inner diameter side.

Therefore, the inner collar section 59 of the press-fitting jig K is setin contact with the step surface G formed by the circumferentialdirection groove. In this state, load (pressing force) in an arrow Edirection (axial direction) of FIG. 1 is applied to the press-fittingjig 55. Consequently, this load can be applied to the outer ring 5through an intermediation of an inner collar section 53 engaged with thestep surface G. The stem shaft 12 of the outer ring 5 can be pressed-fitinto the hole 22 of the hub wheel 1. To apply the axial direction loadto the press-fitting jig K, various axial direction reciprocatingmechanisms such as a press mechanism, a cylinder mechanism, and a ballscrew mechanism can be used. The step surface G can be formed byrecesses disposed at a predetermined pitch along the circumferentialdirection rather than being formed by the circumferential directiongroove. Further, the step surface G may be formed by projected streaksor projections rather than the groove or the recesses.

When the stem shaft 12 is press-fit into the hole 22 of the hub wheel 1in a state of the outer ring 5 alone of the constant-velocity universaljoint 3 illustrated in FIG. 9 or a state in which the outer ring 5, theinner ring 6, the ball 7, and the cage 8 are assembled as illustrated inFIG. 10 rather than a state of a drive shaft assembly, a method ofapplying press-fitting load to an end surface 5 a on the inboard side ofthe outer ring 5 may be adopted. The stem shaft 12 can be press-fitwithout providing the step surface G on the outer diameter surface ofthe outer ring 5. In other words, the jig K1 illustrated in FIG. 8 canbe used. The jig K1 can be formed by a bottomed short cylindricalmember. In other words, the jig K1 includes a main body section 98 madeof a cylindrical member and a bottom wall 99 that blocks the opening onthe inboard side of this main body section 98. In FIGS. 9 and 10, aRzeppa constant-velocity universal joint in which groove bottoms of thetrack grooves 14 and 16 are formed by arc sections is illustrated inFIGS. 9 and 10. Even when the stem shaft 12 is press-fit by the outerring 5 alone or the like in this way, the constant-velocity universaljoint may be other constant-velocity universal joints such as anundercut free type in which the groove bottoms of the track grooves 14and 16 have linear straight sections.

In a state in which the stem shaft 12 of the outer ring 5 is press-fitin the hole 22 of the hub wheel 1, and the stem shaft 12 of the outerring 5 and the hub wheel 1 are integrated through an intermediation ofthe recess-projection fitting structure M, as illustrated in FIG. 6, thecylindrical section 66 projects from the fitting hole 22 a to thetapered hole 22 b side.

Therefore, this cylindrical section 66 is expanded in diameter by usinga jig 67 illustrated in FIGS. 6 to 8. The caulking jig 67 includes acolumnar main body section 67 a and a distal end swelling section 67 bprovided on a distal end surface of this main body section 67 a. In thiscase, the distal end swelling section 67 b can be loosely fit in thecylindrical section 66. An outer circumferential surface of the distalend swelling section 67 b is formed as a gentle radius section on a mainbody section side thereof.

In this case, the distal end swelling section 67 b of the caulking jig67 is fit in the cylindrical section 66. As illustrated in FIGS. 7 and 8and the like, the caulking jig 67 is swung while being pressed in anarrow α direction. The swinging is to swing the caulking jig 67 with adevice axis O as a rotation axis, and with an intersection of a jig axisO1 and the device axis O as a fulcrum such that the jig axis O1 tiltsrelative to the device axis O. Consequently, a circumferential wallsurface of the distal end swelling section 67 b presses an innerdiameter surface of the cylindrical section 66 to an outer diameterside. Therefore, the cylindrical section 66 is plastically deformedoutward in the diameter direction and the expanded-diameter caulkingsection (tapered locking piece) 65 illustrated in FIG. 1 is formed. Theshaft slip-off preventing structure M1 is formed in a hook structure inwhich the cylindrical section 66 provided at the shaft end of the stemshaft 12 is plastically deformed outward in the diameter direction bythe swinging caulking by the swinging caulking jig 67.

In this case, in order to support the outer ring 5 of theconstant-velocity universal joint 3, for example, the jig K illustratedin FIG. 7 and the jig K1 illustrated in FIG. 8 can be used. The jig Kcan receive axial direction load by the swinging caulking through anintermediation of the inner collar section 53 engaged with the stepsurface G. In the jig K1, a main body section 98 is fit in the openingside of the mouth section 11 of the outer ring 5 and an inner surface 99a of a bottom wall 99 is brought into contact with the opening end 11 bof the mouth section 11. In this way, the jib K1 can receive the axialdirection load by the swinging caulking.

Certain degree of load is applied during press fitting (when the stemshaft 12 is press-fit into the hub wheel 1) to strike the back surface11 a of the outer ring 5 of the constant-velocity universal joint 3against the caulking section 31. After the load is removed, contactsurface pressure of a striking section of the back surface 11 a (endsurface 31 a of caulking section 31) is reduced by spring-back of theouter ring 5 of the constant-velocity universal joint 3. When thecylindrical section 66 is caulked, load is applied in the axialdirection. After the caulking, the contact surface pressure of thestriking section of the back surface 11 a (end surface 31 a of caulkingsection 31) can be reduced by spring-back of the stem shaft 12.Therefore, this contact surface pressure can be set to be equal to orlower than 100 MPa.

In the present invention, it is possible to surely form therecess-projection fitting structure M in which the entire fittingcontact regions 38 of the projections 35 of the stem shaft 12 and therecesses 36 of the hub wheel 1 adhere to each other. Moreover, it isunnecessary to form spline sections and the like in a member in whichthe recesses 36 are formed. The bearing device for a wheel is excellentin productivity. Further, phase alignment of the splines is unnecessary.It is possible to realize improvement of assemblability, prevent damageto the tooth surfaces during press fitting, and maintain a stable fitstate.

In the recess-projection fitting structure M, because the entire fittingcontact regions 38 of the projections 35 and the recesses 36 adhere toeach other, a gap in which a backlash occurs is not formed in thediameter direction and the circumferential direction. Therefore, theentire fitting regions contribute to torque transmission, stable torquetransmission is possible, and noise is not caused.

Because the shaft slip-off preventing structure M1 is a hook structurein which the cylindrical section is plastically deformed outward in thediameter direction, screw fastening as in the conventional art can beomitted. Therefore, it is unnecessary to form a screw section projectingfrom the hole 22 of the hub wheel 1 in the stem shaft 12. It is possibleto realize a reduction in weight, omit screw fastening work, and realizeimprovement of assembly workability.

With this shaft slip-off preventing structure M1, it is possible toeffectively prevent the stem shaft 12 of the outer joint member fromslipping off in the axial direction from the hole 22 of the hub wheel 1.Consequently, it is possible to maintain a stable connected state andrealize improvement of a quality of the bearing device for a wheel.Moreover, caulking load during caulking may be relatively small. It ispossible to increase the thickness of this caulking section 65 and bringthe caulking section 65 into press-contact with the hub wheel innerdiameter surface through an intermediation of large press-contact force.Consequently, it is possible to provide a firmer slip-off preventingmechanism (structure). Further, because such a firm slip-off preventingmechanism (structure) M1 is provided, bending rigidity of the stem shaft12 is improved and the stem shaft 12 is robust against bending. If thecaulking load during caulking can be reduced, it is possible to preventdeformation of a region that receives load (load receiving section ofthe outer joint member of the constant-velocity universal joint 3, e.g.,a step surface provided on the outer diameter surface of the outer jointmember and an opening side end surface of the outer joint member).

The caulking section 31 and the back surface 11 a of the mouth section11 of the outer ring 5 are set in contact with each other, wherebybending rigidity in the axial direction is improved, the shaft becomesrobust against bending, and a high-quality product excellent indurability is obtained. Moreover, positioning during press fitting canbe realized by this contact. Consequently, dimension accuracy of thisbearing device for a wheel is stabilized, it is possible to securestable length as axial direction length of the recess-projection fittingstructure M disposed along the axial direction and to realizeimprovement of torque transmission performance. Further, a sealstructure can be configured by this contact. It is possible to preventintrusion of foreign matters into the recess-projection fittingstructure M from this caulking section 31 side. The recess-projectionfitting structure M can maintain a stable fit state over a long periodof time.

Because the end of the hub wheel 1 is caulked and preload is applied tothe roller bearing 2, it is unnecessary to apply preload with the mouthsection 11 of the outer ring 5. Therefore, it is possible to press-fitthe stem shaft 12 of the outer ring 5 without taking into accountpreload and realize improvement of connectability (assemblability) ofthe hub wheel 1 and the outer ring 5.

When the contact surface pressure between the caulking section 31 of thehub wheel 1 and the back surface 11 a of the mouth section 11 exceeds100 MPa, noise is likely to be caused. When torque load is large, adifference occurs in torsion amounts of the outer ring 5 of theconstant-velocity universal joint 3 and the hub wheel 1. Sudden slipoccurs in the contact section of the outer ring 5 of theconstant-velocity universal joint 3 and the hub wheel 1 because of thisdifference and noise occurs. On the other hand, when the contact surfacepressure is equal to or lower than 100 MPa as in the present invention,it is possible to prevent sudden slip from occurring and suppressoccurrence of noise. Consequently, it is possible to configure a silentbearing device for a wheel. Even if the contact surface pressure isequal to or lower than 100 MPa, it is preferable to set the contactsurface pressure to be equal to or higher than surface pressure withwhich a seal structure can be configured.

By providing the pocket section 50 for storing the extruded portion 45caused by recess formation by the press fitting, it is possible to hold(maintain) the extruded portion 45 in this pocket section 50. Theextruded portion 45 does not enter the inside of the vehicle and thelike on the outside of the device. In other words, the extruded portion45 can be kept stored in the pocket section 50. It is unnecessary toperform removal processing for the extruded portion 45. It is possibleto realize a reduction in assembly work man-hour and realize improvementof assembly workability and cost reduction.

By providing the collar section 52 for centering with the hole 22 of thehub wheel 1 on an opposite projection side in the axial direction of thepocket section 50, ejection of the extruded portion 45 in the pocketsection 50 to the guide section side is eliminated. The extruded portion45 is more stably stored. Moreover, because the guide section is usedfor centering, it is possible to press-fit the stem shaft 12 into thehub wheel 1 while preventing decentering. Therefore, it is possible tohighly accurately connect the outer joint member and the hub wheel 1 andperform stable torque transmission.

Further, by arranging the projecting direction intermediate regions ofthe projections 35 on the recess formation surface before recessformation, the projections 35 bite in the recess formation surfaceduring press fitting and the recesses 36 can be surely formed. In otherwords, it is possible to sufficiently secure a press-fitting margin forthe opposite side of the projections 35. Consequently, moldability ofthe recess-projection fitting structure M is stabilized, no fluctuationin press-fitting load occurs, and stable torsion strength can beobtained.

Because the guide section for centering, i.e., the cylindrical section66 is provided in the stem shaft 12, the stem shaft 12 can be press-fitinto the hub wheel 1 without causing decentering to thereby stablyperform formation of the recesses 36 by the projections 35. Therefore,it is possible to highly accurately configure the recess-projectionfitting structure M. Further, because the taper section 22 d canconfigure a guide at the start of press fitting, it is possible to pressfit the stem shaft 12 of the outer ring 5 into the hole 22 of the hubwheel 1 without causing decentering to thereby perform stable torquetransmission.

In the embodiment illustrated in FIG. 1 and the like, the projections 35of the recess-projection fitting structure M is provided in the stemshaft 12 of the outer ring 5, the hardness in the axial direction end ofthe projections 35 is set higher than that of the hole inner diametersection of the hub wheel 1, and the stem shaft 12 is press-fit into thehole 22 of the hub wheel 1. Therefore, it is possible to increase thehardness on the shaft side and improve rigidity of the shaft.

Generation of hoop stress on the bearing raceway surface is suppressedby arranging the recess-projection fitting structure M avoiding aposition right below the raceway surface of the roller bearing 2.Consequently, it is possible to prevent occurrence of deficiencies ofthe bearing such as a reduction in rolling fatigue life, occurrence of acrack, and stress corrosion crack.

As in this embodiment, teeth with a module equal to or smaller than 0.5are used in the spline 41 formed in the stem shaft 12. Therefore, it ispossible to realize improvement of moldability of this spline andrealize a reduction in press-fitting load. Because the projections 35can be formed by a spline normally formed in the shaft of this kind, itis easy to form the projections 35 at low cost.

The outer circumferential surface 25 a of the outer member 25 of thebearing 2 is fit and built in the knuckle 34 on the vehicle body side.The fitting and building-in means that the outer member 25 is completedto be built in the knuckle 34 by fitting the outer member 25 in theknuckle 34. The outer member 25 can be built in the knuckle 34 bypress-fitting, for example, the outer circumferential surface 25 a ofthe cylindrical surface shape of the outer member 25 into thecylindrical inner circumferential surface 34 a of the knuckle 34.

When a diameter difference between the outer diameter dimension D1 ofthe stem shaft 12 and the inner diameter dimension D of the fitting hole22 of the hub wheel 1 is represented as Δd, the height of the projectionis represented as h, and a ratio of the diameter difference and theheight is represented as Δd/2h, a relation among the diameterdifference, the height, and the ratio is 0.3<Δd/2h<0.86. Therefore, itis possible to sufficiently secure a press-fitting margin of theprojections 35. In other words, when Δd/2h is equal to or smaller than0.3, torsion strength falls. If Δd/2h exceeds 0.86, the entireprojections 35 bite in the opposite side because of very smalldecentering and press-fit tilt during press fitting, moldability of therecess-projection fitting structure M is deteriorated, and press-fittingload suddenly increases. When moldability of the recess-projectionfitting structure M is deteriorated, because not only torsion strengthfalls but also an expansion amount of the hub wheel outer diameterincreases, there is a problem in that, for example, the function of thebearing 2 inserted in the hub wheel 1 is affected and rotation life isreduced. On the other hand, by setting Δd/2h to 0.3 to 0.86, moldabilityof the recess-projection fitting structure M is stabilized, fluctuationin press-fitting load is eliminated, and stable torsion strength can beobtained.

Because the taper section 22 d can form a guide at the start of pressfitting, it is possible to press-fit the stem shaft 12 of the outer ring5 into the hole 22 of the hub wheel 1 without causing decentering andperform stable torque transmission. Further, because the outer diameterD4 of the cylindrical section 66 is set smaller than the inner diameterdimension D of the fitting hole 22 a of the hole 22, the cylindricalsection 66 functions as a centering member. Therefore, it is possible topress-fit the stem shaft into the hub wheel while preventing decenteringand perform more stable press fitting.

The stem shaft 12 of the outer ring 5 can be effectively prevented fromslipping off from the hole 22 of the hub wheel 1 (in particular,slipping off in the axial direction to the shaft side) by the shaftslip-off preventing structure M1. Consequently, it is possible tomaintain a stable connection state and realize improvement of a qualityof the bearing device for a wheel. Because the shaft slip-off preventingstructure M1 is the tapered locking piece 65, screw fastening in thepast can be omitted. Therefore, it is unnecessary to form a screwsection projecting to the stem shaft 12 from the hole 22 of the hubwheel 1. It is possible to realize a reduction in weight, omit screwfastening work, and improve assembly workability. Moreover, in thetapered locking piece 65, because a part of the stem shaft 12 of theouter ring 5 only has to be expanded, it is possible to easily performformation of the shaft slip-off preventing structure M1. In the movementof the stem shaft 12 of the outer ring 5 in the reverse joint direction,pressing force in a direction for further press-fitting the stem shaft12 is necessary. Therefore, positional shift in the reverse jointdirection of the stem shaft 12 of the outer ring 5 extremely hardlyoccurs. Even if the stem shaft 12 shifts in this direction, because thebottom of the mouth section 11 of the outer ring comes into contact withthe caulking section 31 of the hub wheel 1, the stem shaft 12 of theouter ring 5 does not slip off from the hub wheel 1.

Note that, because the projections 35 can be formed by a spline normallyformed in a shaft of this type, it is possible to easily form theprojections 35 at low cost.

When the recesses 36 are formed by press-fitting the stem shaft 12 intothe hub wheel 1, work hardening occurs on the recesses 36 side. The workhardening means that, when plastic deformation (plastic working) isapplied to an object, resistance against deformation increases as adegree of deformation increases and the object becomes harder than amaterial not subjected to deformation. Therefore, according to plasticdeformation during press fitting, the inner diameter surface 37 of thehub wheel 1 on the recesses 36 side hardens. It is possible to realizeimprovement of rotation torque transmission performance.

The inner diameter side of the hub wheel 11 is relatively soft.Therefore, it is possible to realize improvement of fittability(adhesiveness) in fitting the projections 35 of the outer diametersurface of the stem shaft 12 of the outer ring 5 in the recesses 36 ofthe hole inner diameter surface of the hub wheel 1. It is possible toaccurately suppress a backlash from occurring in the diameter directionand the circumferential direction.

The end expanded-diameter caulking section (tapered locking piece) 65that engages with the inner diameter surface of the hub wheel 1 (in thiscase, the inner diameter surface of the tapered hole 22 b) through anintermediation of the seal material (seal member configuring theforeign-matter intrusion preventing means W2) is provided further on theoutboard side than the recess-projection fitting structure M. Therefore,it is possible to prevent intrusion of foreign matters from a sidefurther on the outboard side than the recess-projection fittingstructure M.

Further on the inboard side than the recess-projection fitting structureM, the seal structure (foreign-matter intrusion preventing means W1) canbe configured by contact of the outer end surface 31 a of the caulkingsection 31 and the back surface 11 a of the mouth section 11 of theouter ring 5. It is possible to prevent intrusion of foreign mattersfrom the inboard side with this seal structure.

In this way, as in the embodiment, the foreign-matter intrusionpreventing means W1 and W2 are provided further on the inboard side thanthe recess-projection fitting structure M and further on the outboardside than the recess-projection fitting structure M. Intrusion offoreign matters from both end sides in the axial direction of therecess-projection fitting structure M is prevented. Therefore, it ispossible to stably prevent deterioration in adhesiveness over a longperiod of time.

Further, the foreign-matter intrusion preventing means W3 formed byinterposing the seal material is provided between the fitting contactregions 38 of the projections 35 and the recesses 36. Therefore, it ispossible to prevent intrusion of foreign matters between the fittingcontact regions 38 and reliability of foreign-matter intrusionprevention is improved.

During press fitting, axial direction pressing force can be applied tothe outer ring 5 through an intermediation of the step surface G on theouter diameter surface of the outer ring 5 of the constant-velocityuniversal joint 3. In other words, an axial direction pressing forceapplying region can be secured and the vicinity of the stem shaft of theouter ring 5 as the press-fitting shaft can be pressed. Therefore, it ispossible to perform stable press fitting.

A recessed groove may be provided on the outer diameter surface of theouter ring 5 of the constant-velocity universal joint 3 to form adiameter direction end surface of this recessed groove as the stepsurface G. Alternatively, a protrusion may be provided on the outerdiameter surface of the outer ring 5 to form a diameter direction endsurface of this protrusion as the step surface G. In those cases,reliability of securing of the axial direction pressing force applyingregions is improved. As a result, it is possible to perform more stablepress-fitting work.

When the stem shaft 12 is press-fit in a state in which a boot and ashaft are not attached rather than the drive shaft assembly state, ifpress-fitting load is applied to the end surface 5 a on the inboard sideof the outer ring 5 to perform press-fitting work, it is unnecessary toprovide the step surface G on the outer diameter surface of the outerring 5. It is possible to press fit the stem shaft 12 at low cost.

When the cylindrical section 66 is expanded in diameter, the jig 67illustrated in FIG. 11 may be used. This jig 67 includes a columnar mainbody section 68 and a truncated cone section 69 connected to a distalend of this main body section 68. In the truncated cone section 69 ofthe jig 67, a tilt angle of a tilting surface 69 a thereof is setsubstantially the same as a tilt angle of the tapered hole 22 b and anouter diameter of a distal end of the truncated cone section 69 is setto a dimension same as or slightly smaller than the inner diameter ofthe cylindrical section 66. The truncated cone section 69 of the jig 67is fit in through an intermediation of the tapered hole 22 b to applyload in the arrow α direction, whereby diameter expanding force in anarrow β direction in which this cylindrical section 66 increases indiameter is applied to the inner diameter side of the cylindricalsection 66 illustrated in FIG. 6. When the truncated cone 69 of the jig67 is fit in, at least a part of the cylindrical section 66 is pressedto the inner diameter surface side of the tapered hole 22 b and is inpress-contact or contact with the inner diameter surface of the taperedhole 22 b through an intermediation of the seal material configuring theforeign-matter intrusion preventing means W2. Therefore, the shaftslip-off preventing structure M1 can be configured. When load in thearrow α direction of the jig 67 is applied, this bearing device for awheel needs to be fixed not to move in the arrow α direction. However, apart of the hub wheel 1, the constant-velocity universal joint 3, andthe like only has to be received by a fixed member. The inner diametersurface of the cylindrical section 66 may be formed in a tapered shapeincreasing in diameter to the shaft end side. If the inner diametersurface of the cylindrical section 66 is formed into such a shape, it ispossible to mold the inner diameter surface with forging. This leads toa reduction in cost.

Further, in order to reduce load in the arrow α direction of the jig 67,a notch may be cut in the cylindrical section 66 or a conical surface ofthe truncated cone section 69 of the jig 67 may be partially arranged ina circumferential direction. When the notch is cut in the cylindricalsection 66, it is easy to expand the cylindrical section 66 in diameter.When the conical surface of the truncated cone section 69 of the jig 67is partially arranged in the circumferential direction, a region wherethe cylindrical section 66 is expanded in diameter is apart on thecircumference. Therefore, it is possible to reduce push-in load of thejig 67.

Next, FIG. 13 illustrates a second embodiment. In this case, in the hole22 of the hub wheel 1, a stepped surface 22 e extending in the diameterdirection is provided between the tapered hole 22 b and the shaftfitting hole 22 a. The expanded-diameter caulking section 65 engageswith this stepped surface 22 e.

That is, the expanded-diameter caulking section 65 plastically deformedoutward in the diameter direction by swinging caulking by the swingingcaulking jig 67 is molded. That is, the expanded-diameter caulkingsection 65 in this case is folded to bend at a substantially right anglewith respect to the axis of the device. The end surface on the inboardside thereof comes into contact or press-contact with the steppedsurface 22 e.

Other components of the bearing device for a wheel illustrated in FIG.12 are the same as those of the bearing device for a wheel illustratedin FIG. 1. Therefore, the components same as those illustrated in FIG. 1are denoted by the same reference symbols and description of thecomponents is omitted. Therefore, the bearing device for a wheelillustrated in FIG. 13 also realizes operations and effects same asthose of the bearing device for a wheel illustrated in FIG. 1.

FIG. 14 illustrates a third embodiment. The shaft slip-off preventingstructure M1 of this bearing device for a wheel is configured byproviding a tapered locking piece 70 that projects to the outer diameterdirection in a part of the stem shaft 12 rather than forming thecylindrical section 66 illustrated in FIG. 4 in advance.

In this case, a jig 71 illustrated in FIG. 15 is used. The jig 71includes a columnar main body section 72 and a short cylindrical section73 connected to a distal end of this main body section 72. A notch 74 isprovided at a distal end of an outer circumferential surface of theshort cylindrical section 73. Therefore, a distal end wedge section 75is formed in the jig 71. As illustrated in FIG. 16, if the distal endwedge section 75 is driven (load in the arrow α direction is applied), asectional shape of this distal end wedge section 75 is a tiltingsurface, and the outer diameter side of the end of the stem shaft 12 isexpanded in diameter by the notch 74 forming this tilting surface.

Consequently, at least a part of this tapered locking piece 70 comesinto press-contact or contact with the inner diameter surface of thetapered hole 22 b. Therefore, like the tapered locking piece 65illustrated in FIG. 1 and the like, such a tapered locking piece 70 caneffectively prevent the stem shaft 12 of the outer ring 5 from slippingoff in the axial direction from the hole 22 of the hub wheel 1.Consequently, it is possible to maintain a stable connected state andrealize improvement of a quality of the bearing device for a wheel. Aninner diameter surface of the distal end wedge section 75 may be formedin a tapered shape.

FIG. 17 illustrates a fourth embodiment. The shaft slip-off preventingstructure M1 of this bearing device for a wheel is configured by anouter collar-like locking piece 76 formed by caulking a part of the stemshaft 12 to project in the outer diameter direction. In this case, inthe hole 22 of the hub wheel 1, the stepped surface 22 e is providedbetween the fitting hole 22 a and the tapered hole 22 b. The outercollar-like locking piece 76 locks to this stepped surface 22 e.

In this shaft slip-off preventing structure M1, a jig 77 illustrated inFIG. 18 is used. This jig 77 includes a cylindrical member 78. An outerdiameter D5 of the cylindrical member 78 is set larger than an outerdiameter D7 of the end of the stem shaft 12 and an inner diameter D6 ofthe cylindrical member 78 is set smaller than the outer diameter D7 ofthe end of the stem shaft 12.

Therefore, if axes of this jig 77 and the stem shaft 12 of the outerring 5 are aligned and load is applied in the arrow α direction to theend surface 12 a of the stem shaft 12 by an end surface 77 a of the jig77 in this state in which the axes are aligned, as illustrated in FIG.13, an outer circumferential side of the end surface 12 a of the stemshaft 12 is crushed and the outer collar-like locking piece 76 can beformed.

Because the above-mentioned outer collar-like locking piece 76 engageswith the stepped surface 22 e, like the tapered locking piece 65illustrated in FIG. 1 and the like, the outer collar-like locking piece76 can effectively prevent the stem shaft 12 of the outer ring 5 fromslipping off in the axial direction from the hole 22 of the hub wheel 1.Consequently, it is possible to maintain a stable connected state andrealize improvement of a quality of the bearing device for a wheel.

If the jig 77 illustrated in FIG. 18 is used, as illustrated in FIG.20A, the outer collar-like locking piece 76 is formed along acircumferential direction. Therefore, if pressing sections are disposedat a predetermined pitch (e.g., 90° pitch) along the circumferentialdirection as a jig, as illustrated in FIG. 20B, plural outer collar-likelocking pieces 76 are arranged at the predetermined pitch along thecircumferential direction. Even if the plural outer collar-like lockingpiece 76 are arranged at the predetermined pitch along thecircumferential direction as illustrated in FIG. 20B, because the outercollar-like locking pieces 76 locks to the stepped surface 22 e, it ispossible to effectively prevent the stem shaft 12 of the outer ring 5from slipping off in the axial direction from the hole 22 of the hubwheel 1.

As the shaft slip-off preventing structure M1, bolt and nut coupling maybe used as illustrated in FIG. 21 of a fifth embodiment, a lock ring maybe used as illustrated in FIG. 22 of a sixth embodiment, or couplingmeans such as welding may be used as illustrated in FIG. 23 of a seventhembodiment.

In FIG. 21, a screw shaft section 80 is connected to the stem shaft 12and a nut member 81 is screwed on this screw shaft section 80. The nutmember 81 is brought into contact with the stepped surface 22 e of thehole 22. Consequently, the stem shaft 12 is regulated from slipping offfrom the hole 22 of the hub wheel 1 to the shaft side.

In FIG. 22, a shaft extending section 83 is provided further on theoutboard side than the spline 41. A circumferential direction groove 84is provided in this shaft extending section 83 and a lock ring 85 is fitin this circumferential direction groove 84. In the hole 22 of the hubwheel 1 of the stem shaft 12, a step section 22 f to which the lock ring85 locks is provided between the fitting hole 22 a and the tapered hole22 b. Consequently, the lock ring 85 locks to the step section 22 f toregulate the stem shaft 12 from slipping off from the hole 22 of the hubwheel 1 to the shaft side.

In FIG. 23, an end outer circumferential surface of the stem shaft 12and an opening edge on the step surface 22 e side of the fitting hole 22a are joined by welding. Consequently, the stem shaft 12 is regulatedfrom slipping off from the hole 22 of the hub wheel 1 to the shaft side.In this case, a welding region 108 may be disposed over the entirecircumference or may be disposed at a predetermined pitch along thecircumferential direction.

In the bearing device for a wheels illustrated in FIGS. 13, 14, 17, 21,22, 23, and the like, the foreign-matter intrusion preventing means W1,W2, and W3 can be configured. In FIG. 13, the foreign-matter intrusionpreventing means W2 can be formed by interposing the seal materialbetween the expanded-diameter caulking section 65 and the steppedsurface 22 e. In FIG. 14, the foreign-matter intrusion preventing meansW2 can be formed by interposing the seal material between the taperedlocking piece 70 and the inner diameter surface of the tapered hole 22b. In FIG. 17, the foreign-matter intrusion preventing means W2 can beformed by interposing the seal material between the outer collar-likelocking piece 76 and the stepped surface 22 e. In FIG. 22, theforeign-matter instruction preventing means W2 can be formed by the fitlock ring 85. In FIG. 23, the foreign-matter intrusion preventing meansW2 can be formed by the welding region 108 over the entirecircumference. The foreign-matter intrusion preventing means W1 and W3are the same as those in the bearing device for a wheel illustrated inFIG. 1

Further on the inboard side than the recess-projection fitting structureM, the seal structure (foreign-matter intrusion preventing means W1) canbe configured by contact of the outer end surface 31 a of the caulkingsection 31 and the back surface 11 a of the mouth section 11 of theouter ring 5. It is possible to prevent intrusion of foreign mattersfrom the inboard side with this seal structure.

In this way, as in the above-mentioned embodiment, the foreign-matterintrusion preventing means W1 and W2 are provided further on the inboardside than the recess-projection fitting structure M and further on theoutboard side than the recess-projection fitting structure M. Therefore,intrusion of foreign matters from both end sides in the axial directionof the recess-projection fitting structure M is prevented. Therefore, itis possible to more stably prevent deterioration in adhesiveness over along period of time.

Further, because the foreign-matter intrusion preventing means W3 formedby interposing the seal material is provided between the fitting contactregions 38 of the projections 35 and the recesses 36, it is possible toprevent intrusion of foreign matters between the fitting contact regions38. As a result, reliability of foreign-matter intrusion prevention isimproved.

In the bearing device for a wheel according to the present invention, asillustrated in FIG. 24 illustrating a seventh embodiment, the shaftslip-off preventing structure M1 does not have to be provided. In thiscase, as illustrated in FIG. 25, in the circumferential direction groove51, a side 51 a on the spline 41 side is a plane orthogonal to the axialdirection and a side 51 b on an opposite spline side is a taper surfacethat increases in diameter from a groove bottom 51 c to the oppositespline side. A disc-like collar section 52 for centering is providedfurther on the opposite spline side than the side 51 b of thecircumferential direction groove 51. An outer diameter dimension D4 a ofthe collar section 52 is set the same as or slightly smaller than thehole diameter of the fitting hole 22 a of the hole 22. In this case, avery small gap t is provided between an outer diameter surface 52 a ofthe collar section 52 and the inner diameter surface of the fitting hole22 a of the hole 22.

By providing, in the axial direction of the pocket section 50, thecollar section 52 for centering with the hole 22 of the hub wheel 1 onthe opposite projection side, ejection of the extruded portion 45 in thepocket section 50 to the collar section 52 side is eliminated.Therefore, the extruded portion 45 is more stably stored. Moreover,because the collar section 52 is used for centering, it is possible topress-fit the stem shaft 12 into the hub wheel 1 while preventingdecentering. Therefore, it is possible to highly accurately connect theouter ring 5 and the hub wheel 1 and to perform stable torquetransmission.

Because the collar section 52 is used for centering during pressfitting, it is preferable to set an outer diameter dimension thereof toa degree slightly smaller than a hole diameter of the fitting hole 22 aof the hole 22 of the hub wheel 1. If the outer diameter dimension ofthe collar section 52 is the same as or larger than the hole diameter ofthe fitting hole 22 a, the collar section 52 itself is press-fit intothe fitting hole 22 a. When the collar section 52 is press-fit into thefitting hole 22 a, if the collar section 52 and the fitting hole 22 aare decentered, the projections 35 of the recess-projection fittingstructure M are press-fit in this state and the stem shaft 12 and thehub wheel 1 are connected in a state in which the axis of the stem shaft12 and the axis of the hub wheel 1 are not aligned. If the outerdiameter dimension of the collar section 52 is smaller than the holediameter of the fitting hole 22 a, the collar section 52 does notfunction as a section for centering. Therefore, it is preferable to setthe very small gap t between the outer diameter surface 52 a of thecollar section 52 and the inner diameter surface of the fitting hole 22a of the hole 22 to about 0.01 mm to 0.2 mm.

Note that, as illustrated in FIGS. 24 and 25, when the shaft slip-offpreventing structure M1 is not provided, the collar section 52 as thesection for centering of the stem shaft 12 may be omitted.

Next, FIG. 26 is a diagram of a bearing device for a wheel in which thehub wheel 1 and the stem shaft 12 of the outer joint member of theconstant-velocity universal joint 3 fit and inserted in the hole 22 ofthe hub wheel 1 are separably coupled through an intermediation of therecess-projection fitting structure M.

The hub wheel 1 in this case has, as illustrated in FIGS. 26 and 30, thecylinder section 20 and the flange 21 provided at the end on theoutboard side of the cylinder section 20. The hole 22 of the cylindersection 20 has the shaft fitting hole 22 a and the tapered hole 22 b onthe outboard side. An inner wall 22 g projecting in an inner diameterdirection is provided between the shaft fitting hole 22 a and thetapered hole 22 b. A recessed dent section 63 is provided on an endsurface on an opposite shaft fitting hole side of this inner wall 22 g.

The hole 22 has the large diameter section 22 c on an opening sidefurther on an opposite inner wall side than the shaft fitting hole 22 aand a small diameter section 48 further on an inner wall side than theshaft fitting hole 22 a. The taper section 22 d is provided between thelarge diameter section 22 c and the shaft fitting hole 22 a. This tapersection 22 d decreases in diameter along a press-fitting direction incoupling the hub wheel 1 and the stem shaft 12 of the outer ring 5.

A screw hole 64 opening to the end surface on the outboard side isprovided in an axis section of the stem shaft 12 of the outer ring 5. Anopening of the screw hole 64 is formed as a taper section 64 a expandedtoward an opening side. A small diameter section 12 b is provided at theend on the outboard side of the stem shaft 12. In other words, the stemshaft 12 includes a main body section 12 a having a large diameter andthe small diameter section 12 b.

A bolt member 54 is screwed in the screw hole 64 of the stem shaft 12from the outboard side. The bolt member 54 includes, as illustrated inFIGS. 26 and 30, a flanged head 54 a and a screw shaft 54 b. The screwshaft 54 b has a non-screw section 55 a on a proximal end side and ascrew section 55 b on a distal end side. In this case, a through hole 56is provided in the inner wall 22 g, the shaft 54 b of the bolt member 54is inserted through this through hole 56, and the screw section 55 b isscrewed in the screw hole 64 of the stem shaft 12. As illustrated inFIG. 32, a hole diameter D12 of the through hole 56 is set slightlylarger than a shaft diameter (outer diameter) D11 of the non-screwsection 55 a of the shaft 54 b. Specifically, the hole diameter D12 isset such that a difference between the hole diameter D12 and the shaftdiameter D11 is about 0.05 mm<D12−D11<0.5 mm. Note that, a maximum outerdiameter of the screw section 55 b is set the same as or slightlysmaller than the outer diameter of the non-screw section 55 a.

In this bearing device for a wheel, as illustrated in FIG. 27, a shaftpress-fitting guide section M6 for performing guide for press fitting ofthe stem shaft 12 during press fitting is provided on a projectionpress-fitting start side. In this case, the shaft press-fitting guidesection M6 includes a female spline 44 provided in the taper section 22d of the hole 22. That is, as illustrated in FIG. 28A, guiding recesses44 a are provided at a predetermined pitch (in this case, a pitch sameas the arrangement pitch for the projections 35) along thecircumferential direction on the shaft fitting hole 22 a side of thetaper section 22 d.

In this case, as illustrated in FIG. 27, a bottom diameter dimension D16of the guiding recesses 44 a is set larger than the maximum outerdiameter of the projections 35, i.e., the maximum diameter dimension(circumscribed circle diameter) (shaft outer diameter) D1 of the circleconnecting the vertexes of the projections 35 as the projections 41 a ofthe spline 41. As illustrated in FIG. 28A, diameter direction gaps C1are formed between the vertexes of the projections 35 and the bottoms ofthe guiding recesses 44 a.

When this bearing device for a wheel is assembled (when the stem shaft12 of the outer ring 3 of the constant-velocity universal joint ispress-fit in the hub wheel 1), the respective projections 35 of the stemshaft 12 are fit in the respective guiding recesses 44 a of the shaftpress-fitting guide section M6. Consequently, the axis of the hub wheel1 and the axis of the outer ring 5 coincide with each other. When theprojections 35 are fit in the guiding recesses 44 a, because an end onthe recess-projection fitting structure side of the guiding recess 44 ais a flat surface 97 a (see FIG. 27) orthogonal to a press-fittingdirection, the end can receive press-fitting start end surfaces 35 a ofthe projections 35, and the stem shaft 12 can be press-fit from thisstate. When the stem shaft 12 is press-fit, as described above, theinner diameter dimension D of the inner diameter surface 37 of the shaftfitting hole 22 a, the maximum diameter dimension D1 of the projections35, and the outer diameter dimension (diameter dimension) D2 of therecess bottom of the spline 41 are in the relation described above.Moreover, the hardness of the projections 35 is larger than the hardnessof the inner diameter surface 37 by 20 points or more. Therefore, if thestem shaft 12 is press-fit into the hole 22 of the hub wheel 1, theprojections 35 bite in the inner diameter surface 37. The projections 35form the recesses 36, in which the projections 35 fit, along the axialdirection.

After press fitting, the bolt member 54 is screwed in the screw hole 64of the stem shaft 12 from the outboard side. By screwing the bolt member54 in the screw hole 64 of the stem shaft 12 in this way, a flangesection 60 of the head 54 a of the bolt member 54 is fit in the recesseddent section 63 of the inner wall 22 g. Consequently, the hub wheel 1 isnipped by the head 54 a of the bolt member 54 and the recess-projectionfitting structure M or by the head 54 a of the bolt member 54 and thebottom surface (back surface) 11 a of the mouth section 11. The hubwheel 1 and the constant-velocity universal joint 3 are integrated. Inthis way, bolt coupling means M5 on the device axis in which the hubwheel 1 and the stem shaft 12 of the outer ring 5 are connected isformed by the bolt member 54, the screw hole 64 in which this boltmember 54 is screwed, and the like.

In this case, as in the above case, it is preferable to set contactsurface pressure between the caulking section 31 of the hub wheel andthe back surface 11 a of the mouth section 111 a to be equal to or lowerthan 100 MPa. In this embodiment, the gap is provided between the endsurface on the outboard side of the stem shaft 12 and the inner wall 22g. However, the end surface on the outboard side of this stem shaft 12and the inner wall 22 g may be brought into contact with each other. Bybringing the end surface on the outboard side of this stem shaft 12 andthe inner wall 22 g into contact with each other in this way, it becomeseasy to set the contact surface pressure.

In this case, when a diameter difference between the hole diameter D12of the bolt inserting hole 56 and the shaft diameter D11 of thenon-screw section 55 a of the bolt member 54 is represented as Δd5 and adiameter difference in the recess-projection fitting structure M betweenthe outer diameter dimension D1 of the outer ring 5 and the innerdiameter D of the hub wheel 1 is represented as Δd6, a relation betweenthe diameter differences is 0<Δ5d<Δd6.

In this case, as illustrated in FIG. 40, a seal material 100 may beinterposed between a bearing surface 60 a of the bolt member 54 and theinner wall 22 g. For example, the seal material 100 (seal agent) made ofvarious kinds of resin that is hardened after application and candisplay sealing performance between the bearing surface 60 a and thebottom of the recessed dent section 63 of the inner wall 22 g only hasto be applied to the bearing surface 60 a of the bolt member 54. As thisseal material 100, a material that is not deteriorated in an atmospherein which this bearing device for a wheel is used is selected. The sealmaterial 100 may be applied to the inner wall 22 g side or may beapplied to the bearing surface 60 a side and the inner wall 22 g side.

Further, the end surface 31 a of the caulking section 31 and the bottomback surface 11 a of the mouth section 11 are set in contact with eachother. However, as illustrated in FIG. 41, a seal material 200 (sealagent) may be interposed between the end surface 31 a of the caulkingsection 31 and the bottom back surface 11 a of the mouth section 11. Inthis case, the seal material 200 may be applied to the end surface 31 aside, may be applied to the bottom back surface 11 a side, or may beapplied to the end surface 31 a and the bottom back surface 11 a.

In this embodiment, slip-off in the axial direction of the stem shaft 12from the hub wheel 1 is regulated by the bolt coupling means M5. As aresult, it is possible to perform stable torque transmission over a longperiod of time.

By interposing the seal material between the bearing surface 60 a of thebolt member 54, which fixes the hub wheel 1 and the stem shaft 12 of theouter ring 5, and the inner wall 22 g or interposing the seal materialbetween the end surface 31 a of the caulking section 31 and the bottomback surface 11 a of the mouth section 11, intrusion of rainwater andforeign matters into the recess-projection fitting structure M from thisbolt member 54 is prevented and it is possible to realize improvement ofquality.

Incidentally, if the bolt member 54 is removed by screwing back the boltmember 54 from the state illustrated in FIG. 26, the hub wheel 1 can bedrawn out from the outer ring 5. In other words, fitting force of therecess-projection fitting structure M is such that the outer ring 5 canbe drawn out by applying drawing force equal to or larger thanpredetermined force to the outer ring 5.

For example, the hub wheel 1 and the constant-velocity universal joint 3can be separated by a jig 90 illustrated in FIG. 31. The jig 90 includesa base 91, a pressing bolt member 93 screwed in a screw hole 92 of thisbase 91 to be capable of screed in and back, and a screw shaft 96screwed in the screw hole 64 of the stem shaft 12. A through hole 94 isprovided in the base 91. The bolt 33 of the hub wheel 1 is insertedthrough this through hole 94 and a nut member 95 is screwed on this bolt33. When the nut member 95 is screwed on the bolt 33, the base 91 andthe flange 21 of the hub wheel 1 are superimposed and the base 91 isattached to the hub wheel 1.

In this way, after the base 91 has been mounted to the hub wheel 1, orbefore mounting the base 91, the screw shaft 96 is screwed on the screwhole 64 of the stem shaft 12 so that a base section 76 a may protrude tothe out board side from the inner wall 22 g. The protruding amount ofthe base section 96 a is set larger than the axial length of therecess-projection fitting structure M. The screw shaft 96 and thepressing bolt member 93 are arranged in the same axis (on the axis ofthe bearing device for a wheel).

After that, the pressing bolt member 93 is screwed on the screw hole 92of the base 91 from the out board side, and in this state, the boltmember 93 is caused to threadedly advance in the direction of the arrow.In this process, the screw shaft 96 and the pressing bolt member 93 arearranged in the same axis (on the axis of the bearing device for awheel). Therefore, with this threading advancement, the pressing boltmember 93 presses the screw shaft 96 in an arrow direction. This causesthe outer ring 5 to move in the arrow direction with respect to the hubwheel 1, and the hub wheel 1 is removed from the outer ring 5.

Further, in the state in which the outer ring 5 is removed from the hubwheel 1, it is possible to connect the hub wheel 1 and the outer ring 5together again by using, for example, the bolt member 54. That is, as astate in which the base 91 is removed from the hub wheel 1, and thescrew shaft 76 is removed from the stem shaft 12, projections 35 of thestem shaft 12 is fit in the guiding recesses 44 a as illustrated in FIG.34A. Consequently, phases of the male spline 41 on the stem shaft 12side and the female spline 42 of the hub wheel 1 formed by the previouspress-fitting are aligned. When the phases are aligned, as illustratedin FIG. 28A, the diameter direction gaps C1 are formed between thevertexes of the projections 35 and the bottoms of the guiding recesses44 a.

Next, in this state, as illustrated in FIG. 33, the bolt member 54 isscrewed on the screw hole 64 of the stem shaft 12 through anintermediation of the through-hole 56, and the bolt member 54 is causedto threadedly advance with respect to the screw hole 64. As a result, asillustrated in FIG. 34B, the stem shaft 12 is gradually fitted into thehub wheel 1. When the stem shaft 12 fits in the hub wheel 1, the hole 22is slightly expanded in diameter and allows entrance in the axialdirection of the stem shaft 12. The stem shaft 12 enters until thebottom back surface 11 a of the mouth section 11 comes into contact withthe end surface 31 a of the caulking section 31. In this case, at thesame time, as illustrated in FIG. 34C, the end surfaces 35 a of theprojections 35 come into contact with end surfaces 36 a of the recesses36. When the movement in the axial direction is stopped, the hole 22decreases in diameter to return to the original diameter. Consequently,as in the previous press fitting, it is possible to surely configure therecess-projection fitting structure M in which the entire recess fittingregions of the projections 35 adhere to the recesses 36 correspondingthereto.

The opening of the screw hole 64 of the stem shaft 12 is formed as ataper section 50 a opening toward the opening side. Therefore, there isan advantage that the screw shaft 54 b and the bolt member 54 are easilyscrewed in the screw hole 64.

Incidentally, in the first time (press fitting for molding the recesses36 on the inner diameter surface 37 of the hole 22), becausepress-fitting load is relatively large, for press fitting, it isnecessary to use a press machine or the like. On the other hand, inpress fitting in the second time, because press-fitting load is smallerthan the press-fitting load in the first time. Therefore, it is possibleto stably and accurately press-fit the stem shaft 12 into the hole 22 ofthe hub wheel 1 without using the press machine or the like. Therefore,it is possible to separate and connect the outer ring 5 and the hubwheel 1 on the site.

Moreover, when a diameter difference between the hole diameter D12 ofthe bolt inserting hole 56 and the shaft diameter D11 of the non-screwsection 55 a of the bolt member 54 is represented as Δd5 and a diameterdifference between the outer diameter D1 of the outer ring 5 in therecess-projection fitting structure M and the inner diameter dimension Dof the hub wheel 1 in the recess-projection fitting structure M isrepresented as Δd6, a relation between the diameter differences is0<Δd5<Δd6. Therefore, the diameter difference between the hole diameterD12 of the bolt inserting hole 56 and the shaft diameter D11 of thenon-screw section 55 a of the bolt member 54 is set smaller than thediameter difference between the outer diameter D1 of the outer ring 5and the inner diameter dimension D of the hub wheel 1. The boltinserting hole 56 is formed as the shaft press-fitting guide structuresection M3 during re-press fitting of the stem shaft 12 of the outerring 5. In other words, the bolt coupling means M5 includes the shaftpress-fitting guide structure section M3. During re-press fitting, pressfitting of the stem shaft 12 is guided by the shaft press-fitting guidestructure section M3 without being decentered. Therefore, stablere-press fitting is possible. The projections 35 fit in the recesses 36formed previous time without being decentered, whereby it is possible torealize improvement of re-assemblability.

By applying the drawing force in the axial direction to the stem shaft12 of the outer ring 5 in this way, the outer ring 5 can be removed fromthe hole 22 of the hub wheel 1. Therefore, it is possible to realizeimprovement of workability for repairing and inspection(maintainability) of components. Moreover, by press-fitting the stemshaft 12 of the outer ring 5 into the hole 22 of the hub wheel 1 againafter the repairing and inspection of the components, therecess-projection fitting structure M in which the entire fittingcontact regions 38 of the projections 35 and the recesses 36 adhere toeach other can be configured. Therefore, it is possible to configureagain a bearing device for a wheel capable of performing stable torquetransmission.

The shaft press-fitting guide section M6 has the guiding recess 44 a foraligning a phase of the projections 35 and a phase of the other recesses36. Therefore, when the stem shaft 12 of the outer joint member ispress-fit into the hole 22 of the hub wheel 1 again, the stem shaft 12fits in the recesses 36 formed by the previous press fitting and doesnot damage the recesses 36. Therefore, it is possible to highlyaccurately configure again the recess-projection fitting structure M inwhich a gap that causes a backlash is not formed in the diameterdirection and the circumferential direction.

By forming a gap, for example, between the vertexes of the projections35 and the bottoms of the guiding recesses 44 a, the projections 35 canbe easily fit in the guiding recesses 44 a in a pre-press fittingprocess. Moreover, the guiding recesses 44 a do not hinder press-fittingof the projections 35. Therefore, it is possible to realize improvementof assemblability.

When the axial direction length of the through hole 56 is too short, thethrough hole 56 cannot function as a stable guide. Conversely, when theaxial direction length of the through hole 56 is too long, the thicknessdimension of the inner wall 22 g becomes large, whereby the axialdirection length of the recess-projection fitting structure M cannot besecured, and the weight of the hub wheel 1 becomes large. Therefore, itis possible to make various changes taking into account thosedisadvantages.

In the embodiment, as illustrated in FIG. 28A, the diameter directiongaps C1 are formed between the vertexes of the projections 35 and thebottoms of the guiding recesses 44 a. However, as illustrated in FIG.28B, circumferential direction gaps C2 and C2 may be formed between thesides of the projections 35 and the sides of the guiding recesses 44 a.As illustrated in FIG. 28C, the diameter direction gaps C1 may be formedbetween the vertexes of the projections 35 and the bottoms of theguiding recesses 44 a and the circumferential direction gaps C2 may beformed between the sides of the projections 35 and the sides of theguiding recesses 44 a. By forming such gaps, it is possible to easilyfit the projections 35 in the guiding recesses 44 a in the pre-pressfitting process. Moreover, the guiding recesses 44 a do not hinder pressfitting of the projections 35.

In the spline 41 illustrated in FIG. 2, the pitch of the projections 41a and the pitch of the recesses 41 b are set to the same value. Thus, inthe above-mentioned embodiment, as illustrated in FIG. 2B, acircumferential direction thickness L of projecting directionintermediate regions of the projections 35, and a circumferentialdirection dimension L0 in a position corresponding to the intermediateregion between the projections 35 adjacent to each other in thecircumferential direction are substantially the same.

On the other hand, as illustrated in FIG. 35A, a circumferentialdirection thickness L2 of the projecting direction intermediate regionsof the projections 35 may be smaller than a circumferential directiondimension L1 in a position corresponding to the intermediate regionbetween the projections 35 adjacent to each other in the circumferentialdirection. In other words, in the spline 41 formed in the stem shaft 12,the circumferential direction thickness (tooth thickness) L2 of theprojecting direction intermediate regions of the projections 35 is setsmaller than the circumferential direction thickness (tooth thickness)L1 of projecting direction intermediate regions of projections 43 on thehub wheel 1 side that fit in among the projections 35.

Therefore, a sum Σ(B1+B2+B3+ . . . ) of tooth thicknesses of theprojections 35 in the entire circumference on the stem shaft 12 side isset smaller than a sum Σ(A1+A2+A3+ . . . ) of tooth thicknesses of theprojections 43 (projecting teeth) on the hub wheel 1 side. Consequently,it is possible to increase a shearing area of the projections 43 on thehub wheel 1 side and secure torsion strength. Moreover, because thetooth thickness of the projections 35 is small, it is possible to reducepress-fitting load and realize improvement of press-fitting performance.When a sum of circumferential direction thicknesses of the projections35 is set smaller than a sum of circumferential direction thicknesses ofthe projections 43 on the opposite side, it is unnecessary to set thecircumferential direction thickness L2 of all the projections 35 smallerthan the dimension L1 in the circumferential direction between theprojections 35 adjacent to each other in the circumferential direction.In other words, even if the circumferential direction thickness ofarbitrary projections 35 among the plural projections 35 is the same asor larger than a dimension in the circumferential direction between theprojections adjacent to each other in the circumferential direction, asum of circumferential direction thicknesses only has to be smaller thana sum of dimensions in the circumferential direction.

The projections 35 in FIG. 35A are trapezoidal in section. However, ashape of the projections 35 may be an involute tooth shape asillustrated in FIG. 35B.

The shaft press-fitting guide section M6 may be that illustrated in FIG.36. In FIG. 36A, the end on the recess-projection fitting structure Mside of the guiding recess 44 a is a tilting surface 97 b that decreasesin diameter along a press-fitting direction (press-fitting progressdirection). In other words, a tilt angle θ3 of the tilting surface 97 bis, for example, about 45°.

In FIGS. 36B and 36C, a diameter direction depth dimension of theguiding recess 44 a decreases along the press-fitting direction. In FIG.36B, the end on the recess-projection fitting structure M side is theflat surface 97 a orthogonal to the press-fitting direction. In FIG.36C, the end on the recess-projection fitting structure M side is thetilting surface 97 b that decreases in diameter along the press-fittingdirection (press-fitting progress direction).

If the end on the recess-projection fitting structure side of theguiding recess 44 a is the flat surface 97 a orthogonal to thepress-fitting direction, when the stem shaft 12 is press-fit into thehole 22, this flat surface 97 a can receive the stem shaft 12. If theend is the tilting surface 97 b, the projections 35 can be stably fit inthe recesses 36 on the opposite side from the guiding recess 44 a. Evenif the diameter direction depth of the guiding recesses 44 a decreasesalong the press-fitting direction, the projections 35 can be stably fitin the recesses 36 on the opposite side from the guiding recesses 44 a.

Next, FIG. 37 illustrates another embodiment. In this case, the innerwall 22 g is not provided in the hub wheel 1. Instead of this inner wall22 g, a ring member 86 is inserted in the hole 22 of the hub wheel 1. Inother words, a ring fitting notch section 86 is provided in the hole 22of the hub wheel 1 and a ring member 87 is fit in this ring fittingnotch section 86. When the ring member 87 is fit in the ring fittingnotch section 86, the ring member 87 engages with a notch end surface 86a of the ring fitting notch section 81. It is preferable that clearancebetween an outer diameter of the ring member 87 and an inner diameter ofthe ring fitting notch section 81 be reduced as much as possible or thering member 87 is press-fit into the ring fitting notch section 86.

A bolt inserting hole 88 through which the bolt member 54 is inserted isformed in the ring member 87. In this bolt inserting hole 88, as in thebolt inserting hole 56 according to the first embodiment, when adiameter difference between the hole diameter D12 and the shaft diameterD11 of the non-screw section 55 a of the bolt member 54 is representedas Δd5 and a diameter difference between the outer diameter D1 of theouter ring 5 and the inner diameter dimension D of the hub wheel 1 inthe recess-projection fitting structure M is represented as Δd6, arelation between the diameter differences is 0<Δd5<Δd6.

Other components of a bearing device for a wheel illustrated in FIG. 38are the same as those of the bearing device for a wheel illustrated inFIG. 26. Therefore, components same as those in FIG. 26 are denoted bythe same reference symbols and description of the components is omitted.

Therefore, the bearing device for a wheel illustrated in FIG. 38realizes operations and effects same as those of the bearing device fora wheel illustrated in FIG. 26. Moreover, because the bolt insertinghole 88 is formed in the ring member 80 separate from the hub wheel 1,the bolt inserting hole 88 can be highly accurately and stably formed.Even when, for example, the ring member 87 is damaged, the ring member87 can be replaced. It is unnecessary to replace the entire hub wheel 1.Therefore, it is possible to realize a reduction in cost.

In this embodiment, the spline 41 forming the projections 35 is formedon the stem shaft 12 side. Hardening treatment is applied to this spline41 of the stem shaft 12 and the inner diameter surface of the hub wheel1 is not hardened (a row material). On the other hand, as illustrated inFIG. 38, a spline 111 (including projected streaks 111 a and recessedstreaks 111 b) subjected to hardening treatment may be formed on theinner diameter surface of the hole 22 of the hub wheel 1. Hardeningtreatment may not be applied to the stem shaft 12. This spline 111 canalso be formed by various machining methods such as broaching, cutting,pressing, and drawing, which are publicly known and used means. Asthermosetting treatment, various kinds of heat treatment such asinduction hardening, and carburizing and quenching can be adopted.

In this case, the projecting direction intermediate regions of theprojections 35 correspond to positions of the recess forming surfacebefore recess formation (outer diameter surface of the stem shaft 12).In other words, a diameter dimension (minimum diameter dimension of theprojections 35) D8 of a circle connecting the vertexes of theprojections 35 as the projections 111 a of the spline 111 is set smallerthan an outer diameter dimension D10 of the stem shaft 12. A diameterdimension (inner diameter dimension of fitting hole inner diametersurfaces among the projections) D9 of a circle connecting bottoms of therecesses 111 b of the spline 111 is set larger than the outer diameterdimension D10 of the stem shaft 12. In other words, a relation among thediameter dimensions and the outer diameter dimension is D8<D10<D9.

If the stem shaft 12 is press-fit into the hole 22 of the hub wheel 1,the recesses 36 in which the projections 35 on the hub wheel 1 side arefit can be formed on the outer circumferential surface of the stem shaft12 by the projections 35. Consequently, the entire fitting contactregions 38 of the projections 35 and the recesses that fit on theprojections 35 adhere to each other.

The fitting contact regions 38 are ranges B illustrated in FIG. 38B andranges from halfway sections to the tops of the ridges in section of theprojections 35. A gap 112 is formed further on an outer diameter sidethan the outer circumferential surface of the stem shaft 12 between theprojections 35 adjacent to each other in the circumferential direction.

In the bearing device for a wheel illustrated in FIG. 38, as in thebearing device described above, it is preferable to provide the shaftpress-fitting guide section M6. In this case, the guiding recesses 44 bonly have to be provided on the stem shaft 12 side. The diameterdirection gaps C1 can be formed between the vertexes of the projections35 and the bottoms of the guiding recesses 44 a, the circumferentialdirection gaps C2 and C2 can be formed between the sides of theprojections 35 and the sides of the guiding recesses 44 a, or thediameter direction gaps C1 and the circumferential direction gaps C2 andC2 can be formed.

In the case illustrated in FIG. 38, as in the case described above, theextruded portion 45 is formed by press fitting. Therefore, it ispreferable to provide the pocket section 50 that stores this extrudedportion 45. Because the extruded portion 45 is formed on the mouth sideof the stem shaft 12, the pocket section 50 is provided on the hub wheel1 side.

In the bearing device for a wheel in which the projections 35 of therecess-projection fitting structure M are provided on the inner diametersurface 37 of the hole 22 of the hub wheel 1, the hardness of the axialdirection ends of the projections 35 is set higher than that of theouter diameter section of the stem shaft 12 of the outer ring 5, and thestem shaft 12 is press-fit as described above, it is unnecessary toperform hardness treatment (heat treatment) on the stem shaft 12 side.Therefore, the bearing device of vehicle is excellent in productivity ofthe outer joint member (outer ring 5) of the constant-velocity universaljoint.

The embodiments of the present invention have been described. However,the present invention is not limited to the embodiments and variousmodifications of the embodiments are possible. For example, the shape ofthe projections 35 of the recess-projection fitting structure M istriangular in section in the embodiment illustrated in FIG. 2 and istrapezoidal in section in the embodiment illustrated in FIG. 35A.Besides, projections of various shapes such as a semicircular shape, asemi-elliptical shape, and a rectangular shape can be adopted. An area,the number, and a circumferential direction disposing pitch, and thelike of the projections 35 can also be arbitrarily changed. In otherwords, it is unnecessary to form the spline 41 or 111 and form theprojections 41 a or 111 a of this spline 41 or 111 as the projections 35of the recess-projection fitting structure M. The projections 35 may besomething like keys or may form wavy mating surfaces of a curved lineshape. In short, it is sufficient that the projections 35 disposed alongthe axial direction are press-fit into the opposite side, the recesses36 adhering to and fitting in the projections 35 can be formed on theopposite side by the projections 35, the entire fitting contact regions38 of the projections 35 and the recesses that fit in the projections 35adhere to each other, and rotation torque can be transmitted between thehub wheel 1 and the constant-velocity universal joint 3.

The hole 22 of the hub wheel 1 may be a deformed-shape hole such as apolygonal hole other than a circular hole. A sectional shape of the endof the stem shaft 12 fit and inserted into this hole 22 may be adeformed-shape section such as a polygon other than a circular section.Further, when the stem shaft 12 is press-fit into the hub wheel 1, onlypress-fitting start ends of the projections 35 have hardness higher thanthat of the regions where the recesses 36 are formed. Therefore, it isunnecessary to set the hardness of the entire projections 35 high. InFIG. 2 and the like, the gap 40 is formed. However, the projections 35may bite in the inner diameter surface 37 of the hub wheel 1 up to therecesses among the projections 35. As a hardness difference between theprojections 35 side and the side of the recess formation surface formedby the projections 35, as described above, it is preferable to set thehardness difference to be equal to or larger than 20 points in HRC. Aslong as the projections 35 can be press-fit, the hardness difference maybe smaller than 20 points.

The end surfaces (press-fitting start ends) of the projections 35 arethe surfaces orthogonal to the axial direction in the embodiments.However, the end surfaces may be surfaces tilting at a predeterminedangle with respect to the axial direction. In this case, the endsurfaces may tilt to the opposite projection side from the innerdiameter side to the outer diameter side or may tilt to the projectionside.

A shape of the pocket section 50 only has to be a shape that can store(house) the extruded portion 45 to be caused. Therefore, a capacity ofthe pocket section 50 only has to be capable of storing the extrudedportion 45 to be caused.

Further, it is also possible to provide small recesses arranged at apredetermined circumferential pitch in the inner diameter surface 37 ofthe hole 22 of the hub wheel 1. It is necessary for the small recessesto have a volume smaller than that of the recesses 36. By thus providingthe small recesses, it is possible to improve the press-fitting propertyof the projections 35. That is, by thus providing the small recesses, itis possible to reduce the capacity of the extruded portion 45 formedduring press fitting of the projections 35, and hence it is possible toreduce the press-fitting resistance. Further, because the extrudedportion 45 can be made smaller, it is possible to reduce the volume ofthe pocket section 50, making it possible to improve the processabilityof the pocket section 50 and the strength of the stem shaft 12. Thesmall recesses may be of various shapes such as a triangular, asemi-elliptical, or a rectangular shape, and the number of small recesscan also be set arbitrarily.

While welding is adopted as the coupling means illustrated in FIG. 23,it is also possible to adopt adhesive instead of welding. Further, it isalso possible to use rollers as the rolling elements 30 of the bearing2. Further, while in the above-mentioned embodiment the third generationbearing device for a wheel is described, it is also possible to adoptthe first or second generation bearing device for a wheel. Note that,when press fitting the projections 35, it is possible to move the memberon which the projections 35 are formed, with the member in which therecesses 36 are formed being stationary. Conversely, it is also possibleto move the member in which the recesses 36 are formed, with the memberon which the projections 35 are formed being stationary. Further, it isalso possible to move both of them. Note that, in the constant-velocityuniversal joint 3, the inner ring 6 and the shaft 10 may be integratedwith each other through the intermediation of the recess-projectionfitting structure M as described with reference to the above-mentionedembodiments.

The seal material interposed between the bearing surface 60 a of thebolt member 54, which fixes by a bolt the hub wheel 1 and the stem shaft12, and the inner wall 22 g is formed by applying the resin to thebearing surface 60 a side of the bolt member 54 in the embodiments.However, conversely, the resin may be applied to the inner wall 22 gside. The resin may be applied to the bearing surface 60 a side and theinner wall 22 g side. When the bolt member 54 is screwed in, if thebearing surface 60 a of the bolt member 54 and the bottom surface of therecessed dent section 63 of the inner wall 22 g are excellent inadhesiveness, such a seal material can also be omitted. In other words,it is possible to improve adhesiveness of the bolt member 54 with thebearing surface 60 a by grinding the bottom surface of the recessed dentsection 63. It goes without saying that, even if the bottom surface ofthe recessed dent section 63 is not ground and is in a so-called turningfinish state, the seal material can be omitted as long as adhesivenesscan be exerted.

As the guiding recesses 44 a, as illustrated in FIGS. 28A, 28B, and 28C,the gaps C1 and C2 are formed among the projections 35. A dimension ofthose gaps only has to be a dimension that does not cause decenteringand shaft misalignment during press fitting and prevents the projections35 from coming into press-contact with the inner surfaces of the guidingrecesses 44 a to cause an increase in press-fitting load. The axialdirection length of the guiding recesses 44 a can be arbitrarily set. Ifthe guiding recesses 44 a are long in the axial direction, this ispreferable in alignment. However, an upper limit of the axial directionlength is limited because of the axial direction length of the hole 22of the hub wheel 1. Conversely, if the axial direction length of thehole 22 of the hub wheel 1 is small, the guiding recesses 44 a do notfunction as a guide and decentering and shaft misalignment are likely tooccur. Therefore, it is necessary to determine the axial directionlength of the guiding recesses 44 a taking into account those points.

A sectional shape of the guiding recesses 44 a is not limited to thatillustrated in FIG. 4 as long as the projections 35 can fit in theguiding recesses 44 a. The sectional shape can be variously changedaccording to a sectional shape and the like of the projections 35. Thenumber of guiding recesses 44 a does not have to be the same as thenumber of projections 35 and may be smaller or larger than the number ofprojections 35. In short, several projections 35 only have to fit inseveral guiding recesses 44 a and a phase of the projections 35 and aphase of the recesses 36 formed in the previous press fitting only haveto coincide with each other.

The tilt angle θ3 of the tilting surfaces 97 b of the ends of theguiding recesses 44 a and the tilt angle θ4 of the bottoms of theguiding recesses 44 a can also be arbitrarily changed. If the tilt angleθ3 of the tilting surfaces 97 b is close to 90°, the tilting surfaces 97b are functionally the same as the flat surfaces 97 a orthogonal to thepress-fitting direction. If the tilt angle θ3 is small, the guidingrecesses 44 a are long and the axial direction length of therecess-projection fitting structure M is small. If the tilt angle θ1 ofthe bottoms is large, it is difficult to form the guiding recesses 44 a.Conversely, if the tilt angle θ1 is small, the function of the tiltedguiding recesses 44 a cannot be exerted. Therefore, it is necessary toset the tilt angles θ3 and θ4 taking into account those points.

The outer member 25 of the roller bearing 2 in the embodiments does notinclude a vehicle body attachment flange. However, the outer member 25may include the vehicle body attachment flange.

INDUSTRIAL APPLICABILITY

The present invention can be applied to bearing devices for a wheel ofthe first generation having the structure in which roller bearings indouble rows are independently used, the second generation in which avehicle body attachment flange is integrally provided in an outermember, the third generation in which an inner raceway surface on oneside of the roller bearings in double rows is integrally formed with anouter circumference of a hub wheel integrally having a wheel attachmentflange, and the fourth generation in which a constant-velocity universaljoint is integrated with the hub wheel and an inner raceway surface ofthe other side of the roller bearings in double rows is integrallyformed with an outer circumference of an outer joint member configuringthe constant-velocity universal joint.

1-18. (canceled)
 19. A bearing device for a wheel, the bearing devicecomprising: a rolling bearing; and a constant velocity universal jointhaving an outer joint member with a shaft section and a mouth section,wherein the rolling bearing comprises: an outer member having an innercircumference in which outer raceway surfaces in double rows are formed;an inner member that has, on an outer circumference thereof, innerraceway surfaces in double-rows opposed to the outer raceway surfaces,the inner member comprising an inner ring and a hub wheel having a holeand a flange for attachment to the wheel; and rolling elements in doublerows interposed between the outer raceway surfaces of the outer memberand the inner raceway surfaces of the inner member, wherein the shaftsection of the outer joint member of the constant-velocity universaljoint is fit and coupled to an inner diameter of the hole of the hubwheel, an axially extending projection provided on an outer diametersurface of the shaft section of the outer joint member is press-fittedalong the axial direction into a small recess provided on an innerdiameter surface of the hole of the hub wheel, and a recess is formed inthe hole of the hub wheel by cutting the small recess by the projectionpress-fitted into the small recess, to thereby form a recess-projectionfitting structure in which an entire fitting contact regions of theprojection and recess adhere to each other, a surface of the recess isformed as cut surface by the projection cutting during the press fittingof the projection, the hub wheel has an end on an inboard side of thehub wheel that is caulked to an outer diameter side to form a caulkingsection, the inner ring of the rolling bearing is externally fit to thehub wheel and fixed by the caulking section, preload being applied tothe rolling bearing, and the caulking section and a back surface of themouth section of the outer joint member of the constant-velocityuniversal joint opposed to the caulking section are in contact with eachother.
 20. A bearing device for a wheel according to claim 19, wherein aguiding recess for performing guide for press fitting of the stem shaftduring press fitting of the projection is provided on an end of aprojection press-fitting start side of the hole of the hub wheel.
 21. Abearing device for a wheel according to claim 20, wherein a diameterdirection gap and a circumferential direction gap are formed between theprojection and the guiding recess in which the projection is fitted. 22.A manufacturing method for a bearing device for a wheel, the bearingdevice comprising: a rolling bearing; and a constant velocity universaljoint having an outer joint member with a shaft section and mouthsection, wherein the rolling bearing comprises: an outer member havingan inner circumference in which outer raceway surfaces in double rowsare formed; an inner member that has, on an outer circumference thereof,inner raceway surfaces in double-rows opposed to the outer racewaysurfaces, the inner member comprising an inner ring and a hub wheelhaving a hole and a flange for attachment to the wheel; and rollingelements in double rows interposed between the outer raceway surfaces ofthe outer member and the inner raceway surfaces of the inner member,wherein the shaft section of the outer joint member of theconstant-velocity universal joint is fit and coupled to an innerdiameter of the hole of the hub wheel, the hub wheel has an end on aninboard side of the hub wheel that is caulked to an outer diameter sideto form a caulking section, the inner ring of the rolling bearing isexternally fit to the hub wheel and fixed by the caulking section,preload being applied to the rolling bearing, and the caulking sectionand a back surface of the mouth section of the outer joint member of theconstant-velocity universal joint opposed to the caulking section are incontact with each other, the method comprises steps of: providing aprojection with an outer diameter surface of the shaft section of theouter joint member, the projection being extended in axially; providinga small recess with the hole of the hub wheel; and forming a recess onthe inner diameter surface of the hole of the hub wheel by cutting thesmall recess by the projection press-fitted into the small recess alongan axial direction, to thereby form a recess-projection fittingstructure in which an entire fitting contact regions of the projectionand recess adhere to each other.
 23. A manufacturing method for abearing device for a wheel according to claim 22, wherein the hub wheeland the shaft section of the outer joint member are fixed through a boltcoupling means comprising a screw hole and a bolt member screwed on thescrew hole of the shaft section, and wherein the method furthercomprises steps of: separating, under a state in which the bolt memberis removed from the screw hole, the recess-projection fitting structureby applying a drawing force in the axial direction; and press-fittingthe projection into the recess by screwing a bolt member on the screwhole of the shaft section to thereby form the recess-projection fittingstructure.